arm: Enable no-writeback vldr.16/vstr.16.

arm: Enable no-writeback vldr.16/vstr.16.

There was previously no way to specify that a register operand cannot
have any writeback modifiers, and as a result the argument to vldr.16
and vstr.16 could be erroneously output with post-increment. This
change adds a constraint which forbids all writeback, and
selects it in the relevant case for vldr.16 and vstr.16

gcc/ChangeLog:

	PR target/96682
	* config/arm/arm-protos.h (arm_coproc_mem_operand_no_writeback):
	Declare prototype.
	(arm_mve_mode_and_operands_type_check): Declare prototype.
	* config/arm/arm.c (arm_coproc_mem_operand): Refactor to use
	_arm_coproc_mem_operand.
	(arm_coproc_mem_operand_wb): New function to cover full, limited
	and no writeback.
	(arm_coproc_mem_operand_no_writeback): New constraint for memory
	operand with no writeback.
	(arm_print_operand): Extend 'E' specifier for memory operand
	that does not support writeback.
	(arm_mve_mode_and_operands_type_check): New constraint check for
	MVE memory operands.
	* config/arm/constraints.md: Add Uj constraint for VFP vldr.16
	and vstr.16.
	* config/arm/vfp.md (*mov_load_vfp_hf16): New pattern for
	vldr.16.
	(*mov_store_vfp_hf16): New pattern for vstr.16.
	(*mov<mode>_vfp_<mode>16): Remove MVE moves.

gcc/testsuite/ChangeLog:

	PR target/96682
	* gcc.target/arm/mve/intrinsics/mve-vldstr16-no-writeback.c: New test.

(cherry picked from commit 9f6abd2db90151c8966d2d2718ab8c299abf1105)