morello: Fix encoding of ldtr/sttr

morello: Fix encoding of ldtr/sttr

This patch fixes the encoding of the immediate in the A64C ldtr/sttr
instructions. Prior to this patch, GAS would accept immediates for these
instructions that were not multiples of 16, and would not scale the
immediate by 16.

gas/ChangeLog:

2021-09-24  Alex Coplan  <alex.coplan@arm.com>

	* testsuite/gas/aarch64/morello_ldst-c64.d: Update following
	test + encoding change.
	* testsuite/gas/aarch64/morello_ldst-invalid.d: New test.
	* testsuite/gas/aarch64/morello_ldst-invalid.l: New test.
	* testsuite/gas/aarch64/morello_ldst-invalid.s: New test.
	* testsuite/gas/aarch64/morello_ldst.d: Update following
	test + encoding change.
	* testsuite/gas/aarch64/morello_ldst.s: Update to use valid
	immediates for ldtr/sttr instructions.

opcodes/ChangeLog:

2021-09-24  Alex Coplan  <alex.coplan@arm.com>

	* aarch64-tbl.h (aarch64_opcode_table): Update A64C_INSNs
	ldtr/sttr to take A64C_ADDR_SIMM9 instead of ADDR_SIMM9
	operands.