Add missing -fno-fast-math.

From-SVN: r86150

gcc/testsuite/gcc.dg/mips-nmadd-2.c

 /* { dg-do compile { target "mips*-*-*" } } */
-/* { dg-options "-O2 -mips4" } */
+/* { dg-options "-O2 -fno-fast-math -mips4" } */
 /* { dg-final { scan-assembler "nmadd.s" } } */
 /* { dg-final { scan-assembler "nmadd.d" } } */
 /* { dg-final { scan-assembler "nmsub.s" } } */