[AArch64] Merge SVE ternary FP operations

[AArch64] Merge SVE ternary FP operations

This patch combines the four individual fused multiply-add optabs
into one pattern and uses unspecs instead of rtx codes.  This is
part of a series of patches that change the SVE FP patterns so that
they can describe cases in which the predicate isn't all-true.

2019-08-07  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64-sve.md (fma<mode>4, *fma<mode>4)
	(fnma<mode>4, *fnma<mode>4, fnms<mode>4, *fnms<mode>4)
	(fms<mode>4, *fms<mode>4): Replace with...
	(<SVE_COND_FP_TERNARY:optab><SVE_F:mode>4)
	(*<SVE_COND_FP_TERNARY:optab><SVE_F:mode>4): ...these new patterns.
	Use unspecs instead of rtx codes.
	(cond_<optab><mode>, *cond_<optab><mode>_2, *cond_<optab><mode>_4)
	(*cond_<optab><mode>_any): Add the predicate to SVE_COND_FP_TERNARY.

From-SVN: r274189