improve package name conversion to makefile variable

No need to call sed here, as tr already does exactly what we want to,
just by extending the expression passed to it.

mk/build.mk

@@ -188,7 +188,7 @@ kernelconfig:
 newpackage:
 	@echo "Creating new package $(PKG)"
 	$(CP) $(TOPDIR)/package/.template $(TOPDIR)/package/$(PKG)
-	pkg=$$(echo $(PKG)|tr '[:lower:]' '[:upper:]'|sed -e "s/-/_/g"); \
+	pkg=$$(echo $(PKG)|tr '[:lower:]-' '[:upper:]_'); \
 		$(SED) "s#@UPKG@#$$pkg#" $(TOPDIR)/package/$(PKG)/Makefile
 	$(SED) 's#@PKG@#$(PKG)#' $(TOPDIR)/package/$(PKG)/Makefile
 	$(SED) 's#@VER@#$(VER)#' $(TOPDIR)/package/$(PKG)/Makefile