[AArch64] Add support for SVE HF vconds

[AArch64] Add support for SVE HF vconds

We were missing vcond patterns that had HF comparisons and HI or HF data.

2019-08-14  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/iterators.md (SVE_HSD): New mode iterator.
	(V_FP_EQUIV, v_fp_equiv): Handle VNx8HI and VNx8HF.
	* config/aarch64/aarch64-sve.md (vcond<mode><v_fp_equiv>): Use
	SVE_HSD instead of SVE_SD.

gcc/testsuite/
	* gcc.target/aarch64/sve/vcond_17.c: New test.
	* gcc.target/aarch64/sve/vcond_17_run.c: Likewise.

From-SVN: r274420