aarch64: Avoid using mismatched ZERO ZA sizes

aarch64: Avoid using mismatched ZERO ZA sizes

The svzero_mask_za intrinsic tried to use the shortest combination
of .b, .h, .s and .d tiles, allowing mixtures of sizes where necessary.
However, Iain S pointed out that LLVM instead requires the tiles to
have the same suffix.  GAS supports both versions, so this patch
generates the LLVM-friendly form.

gcc/
	* config/aarch64/aarch64.cc (aarch64_output_sme_zero_za): Require
	all tiles to have the same suffix.

gcc/testsuite/
	* gcc.target/aarch64/sme/acle-asm/zero_mask_za.c (zero_mask_za_ab)
	(zero_mask_za_d7, zero_mask_za_bf): Expect a list of .d tiles instead
	of a mixture.