[ARM] libm: use s_fma and s_fmaf with hard float instructions

Summary:
s_fmal was included in this change due to needing a bit of
extra work even though Android currently treats double longs
as longs. For this reason, s_fmal is currently unused.

Instead of using bsd style aliasing for fmal in fma, _fmal is
defined by s_fmal.S, then s_fma.S is inherited with a matching
ENTRY and END.

Test Plan: ...

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D501