config: tidy-up of config targets

Introduce two local variables for 'conf' and 'mconf' binaries.
Use $^ automatic variable to invoke [m]conf tool.

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

Makefile.in

@@ -54,13 +54,16 @@ include $(top_srcdir)extra/locale/Makefile.in
 # last included to catch all the objects added by others (locales/threads)
 include $(top_srcdir)libc/Makefile.in
 
+conf := $(top_builddir)extra/config/conf
+mconf := $(top_builddir)extra/config/mconf
+
 ifeq ($(HAVE_DOT_CONFIG),y)
 # If the .config changes then we have to make sure that our includes are
 # updated properly. This would normally work by saying that the headers
 # have uClibc_config.h as prerequisite but since we _symlink_ the headers
 # and do not (?) want to rely on 'make -L' we better update them right here,
 # on spot to save us from alot of hazzle.
-$(top_builddir)include/bits/uClibc_config.h: $(top_builddir)extra/config/conf $(KCONFIG_CONFIG) $(top_srcdir)extra/scripts/conf-header.sh | $(top_builddir)include/bits $(top_builddir)include/config
+$(top_builddir)include/bits/uClibc_config.h: $(conf) $(KCONFIG_CONFIG) $(top_srcdir)extra/scripts/conf-header.sh | $(top_builddir)include/bits $(top_builddir)include/config
 	@$(disp_gen)
 	$(Q)@$< -s $(top_srcdir)extra/Configs/Config.in
 	$(Q)$(top_srcdir)extra/scripts/conf-header.sh $(KCONFIG_CONFIG) > $@
@@ -416,40 +419,39 @@ $(addprefix $(top_builddir),include include/bits include/sys include/config lib
 
 # configuration
 # ---------------------------------------------------------------------------
-$(top_builddir)extra/config/conf $(top_builddir)extra/config/mconf: | $(top_builddir)include/config $(top_builddir)extra/config/lxdialog
+$(conf) $(mconf): | $(top_builddir)include/config $(top_builddir)extra/config/lxdialog
 	$(Q)$(MAKE) -C extra/config $(@F)
 
-menuconfig: $(top_builddir)extra/config/mconf
-	$(Q)$(top_builddir)extra/config/mconf extra/Configs/Config.in
+menuconfig: $(mconf)
+	$(Q)$< extra/Configs/Config.in
 
-config: $(top_builddir)extra/config/conf
-	$(Q)$(top_builddir)extra/config/conf extra/Configs/Config.in
+config: $(conf)
+	$(Q)$< extra/Configs/Config.in
 
-oldconfig: $(top_builddir)extra/config/conf
-	$(Q)$(top_builddir)extra/config/conf -o extra/Configs/Config.in
+oldconfig: $(conf)
+	$(Q)$< -o extra/Configs/Config.in
 
-silentoldconfig: $(top_builddir)extra/config/conf
-	$(Q)$(top_builddir)extra/config/conf -s extra/Configs/Config.in
+silentoldconfig: $(conf)
+	$(Q)$< -s extra/Configs/Config.in
 
-randconfig: $(top_builddir)extra/config/conf
-	$(Q)$(top_builddir)extra/config/conf -r extra/Configs/Config.in
+randconfig: $(conf)
+	$(Q)$< -r extra/Configs/Config.in
 
-allyesconfig: $(top_builddir)extra/config/conf
-	$(Q)$(top_builddir)extra/config/conf -y extra/Configs/Config.in
+allyesconfig: $(conf)
+	$(Q)$< -y extra/Configs/Config.in
 	$(SED) -i -e "s/^DODEBUG=.*/# DODEBUG is not set/" \
 		-e "s/^DOASSERTS=.*/# DOASSERTS is not set/" \
 		-e "s/^SUPPORT_LD_DEBUG_EARLY=.*/# SUPPORT_LD_DEBUG_EARLY is not set/" \
 		-e "s/^SUPPORT_LD_DEBUG=.*/# SUPPORT_LD_DEBUG is not set/" \
 		-e "s/^UCLIBC_MJN3_ONLY=.*/# UCLIBC_MJN3_ONLY is not set/" \
 		$(KCONFIG_CONFIG)
-	$(Q)$(top_builddir)extra/config/conf -o extra/Configs/Config.in
+	$(Q)$< -o extra/Configs/Config.in
 
-allnoconfig: $(top_builddir)extra/config/conf
-	$(Q)$(top_builddir)extra/config/conf -n extra/Configs/Config.in
+allnoconfig: $(conf)
+	$(Q)$< -n extra/Configs/Config.in
 
-defconfig: $(top_builddir)extra/config/conf
-	$(Q)$(top_builddir)extra/config/conf \
-		-D extra/Configs/defconfigs/$(ARCH) extra/Configs/Config.in
+defconfig: $(conf)
+	$(Q)$< -D extra/Configs/defconfigs/$(ARCH) extra/Configs/Config.in
 
 menuconfig-clean-y:
 	$(Q)$(MAKE) -C extra/config CLEAN_extra/config