Remove duplicated -frounding-math

No need to add -frounding-math.  math-flags in Makeconfig includes
-frounding-math.

	* math/Makefile (CFLAGS-test-float.c): Remove -frounding-math.
	(CFLAGS-test-double.c): Likewise.
	(CFLAGS-test-ldouble.c): Likewise.
	(CPPFLAGS-test-ifloat.c): Likewise.
	(CPPFLAGS-test-idouble.c): Likewise.
	(CPPFLAGS-test-ildoubl.c): Likewise.
	(CFLAGS-test-test-fenv.c): Remove variable.
	(CFLAGS-test-misc.c): Likewise.