[AArch64][SVE] Fix IFN_COND_FMLA movprfx alternative

[AArch64][SVE] Fix IFN_COND_FMLA movprfx alternative

This patch fixes a cut-&-pasto in the (match_dup 4) version of
"cond_<SVE_COND_FP_TERNARY:optab><SVE_F:mode>".  (It's a shame
that there's so much cut-&-paste in these patterns, but it's hard
to avoid without more infrastructure.)

2018-12-20  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64-sve.md (*cond_<optab><mode>_4): Use
	sve_fmla_op rather than sve_fmad_op for the movprfx alternative.

gcc/testsuite/
	* gcc.target/aarch64/sve/fmla_2.c: New test.
	* gcc.target/aarch64/sve/fmla_2_run.c: Likewise

From-SVN: r267303