SPARC: Remove subtarget checks on setLibcallImpl (#147667)
Remove the subtarget dependent useSoftMulDiv check on the mul/div
libcall configuration. The libcall still needs to exist with the
given ABI for the module regardless of the subtarget dependent
lowering decision which is separately controlled.
Also the f128<->i64 conversion calls were set twice, so eliminate
the redundant setting and always do it for sparc32.
