arm: Fix constant immediates predicates and constraints for some MVE builtins

arm: Fix constant immediates predicates and constraints for some MVE builtins

Several MVE builtins incorrectly use the same predicate/constraint
pair for several modes, which does not match the specification.
This patch uses the appropriate iterator instead.

2022-09-06  Christophe Lyon  <christophe.lyon@arm.com>

	gcc/
	* config/arm/mve.md (mve_vqshluq_n_s<mode>): Use
	MVE_pred/MVE_constraint instead of mve_imm_7/Ra.
	(mve_vqshluq_m_n_s<mode>): Likewise.
	(mve_vqrshrnbq_n_<supf><mode>): Use MVE_pred3/MVE_constraint3
	instead of mve_imm_8/Rb.
	(mve_vqrshrunbq_n_s<mode>): Likewise.
	(mve_vqrshrntq_n_<supf><mode>): Likewise.
	(mve_vqrshruntq_n_s<mode>): Likewise.
	(mve_vrshrnbq_n_<supf><mode>): Likewise.
	(mve_vrshrntq_n_<supf><mode>): Likewise.
	(mve_vqrshrnbq_m_n_<supf><mode>): Likewise.
	(mve_vqrshrntq_m_n_<supf><mode>): Likewise.
	(mve_vrshrnbq_m_n_<supf><mode>): Likewise.
	(mve_vrshrntq_m_n_<supf><mode>): Likewise.
	(mve_vqrshrunbq_m_n_s<mode>): Likewise.
	(mve_vsriq_n_<supf><mode): Use MVE_pred2/MVE_constraint2 instead
	of mve_imm_selective_upto_8/Rg.
	(mve_vsriq_m_n_<supf><mode>): Likewise.