Remove ldbl-128/s_fma.c - it makes no sense to use emulated float128
operations to emulate FMA. Benchmarking shows dbl-64/s_fma.c is about
twice as fast. Remove redundant dbl-64/s_fma.c includes in targets
that were trying to work around this issue.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>