[binutils-gdb] [AArch64] Use "must" rather than "should" in error messages

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT ab3b8fcfdb06695d27eaec4eedb019ada4a5713e ***

Author: Richard Sandiford <richard.sandiford@arm.com>
Branch: master
Commit: ab3b8fcfdb06695d27eaec4eedb019ada4a5713e

[AArch64] Use "must" rather than "should" in error messages

One of the review comments from the SVE series was that it would
be better to use "must" rather than "should" in error messages.
I think this patch fixes all cases in the AArch64 code.
It also uses "must be" instead of "expected to be".

opcodes/
	* aarch64-opc.c (operand_general_constraint_met_p): Use "must be"
	rather than "should be" or "expected to be" in error messages.

gas/
	* config/tc-aarch64.c (output_operand_error_record): Use "must be"
	rather than "should be" or "expected to be" in error messages.
	(parse_operands): Likewise.
	* testsuite/gas/aarch64/diagnostic.l: Likewise.
	* testsuite/gas/aarch64/legacy_reg_names.l: Likewise.
	* testsuite/gas/aarch64/sve-invalid.l: Likewise.
	* testsuite/gas/aarch64/sve-reg-diagnostic.l: Likewise.