math.h: Set HAVE_HW_FMA32 based on compiler provided macro

Fixes sin/cos piglits on non-FMA capable asics.
Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=35983



Reviewer: Tom Stellard
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
llvm-svn: 323677