arm: Remove unsigned variant of vcaddq_m

arm: Remove unsigned variant of vcaddq_m

The unsigned variants of the vcaddq_m operation are not needed within the
compiler, as the assembly output of the signed and unsigned versions of the
ops is identical: with a `.i` suffix (as opposed to separate `.s` and `.u`
suffixes).

Tested with baremetal arm-none-eabi on Arm's fastmodels.

gcc/ChangeLog:

	* config/arm/arm-mve-builtins-base.cc (vcaddq_rot90, vcaddq_rot270):
	Use common insn for signed and unsigned front-end definitions.
	* config/arm/arm_mve_builtins.def
	(vcaddq_rot90_m_u, vcaddq_rot270_m_u): Make common.
	(vcaddq_rot90_m_s, vcaddq_rot270_m_s): Remove.
	* config/arm/iterators.md (mve_insn): Merge signed and unsigned defs.
	(isu): Likewise.
	(rot): Likewise.
	(mve_rot): Likewise.
	(supf): Likewise.
	(VxCADDQ_M): Likewise.
	* config/arm/unspecs.md (unspec): Likewise.
	* config/arm/mve.md: Fix minor typo.