test/math: add fallback to libm-test-ulps-generic logic

Under test/math/, there is libm-test-ulps-generic used as fallback
in case that libm-test-ulps-$(TARGET_ARCH) does not exist.

This is required for arches that don't have ULPS yet.

Original patch from Jian Peng was found here:
http://lists.uclibc.org/pipermail/uclibc/2011-April/045172.html

Signed-off-by: Jian Peng <jipeng2005@gmail.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Anton Kolesov <akolesov@synopsys.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

test/math/Makefile.in

@@ -31,7 +31,7 @@ PERL := /usr/bin/perl
 MDEPS := $(wildcard test-*.c)
 $(MDEPS): libm-test.c
 
-TARGET_ULP := $(TARGET_ARCH)
+TARGET_ULP := $(if $(wildcard libm-test-ulps-$(TARGET_ARCH)),$(TARGET_ARCH),generic)
 ULP_SUFFIX :=
 ifeq ($(TARGET_ARCH),mips)
 ULP_SUFFIX:=$(if $(CONFIG_MIPS_ISA_MIPS64R1)$(CONFIG_MIPS_ISA_MIPS64R2),64,32)