arm: [MVE intrinsics] factorize vshllbq vshlltq

Factorize vshllbq vshlltq so that they use the same pattern.

2022-09-08  Christophe Lyon  <christophe.lyon@arm.com>

	gcc/
	* config/arm/iterators.md (mve_insn): Add vshllb, vshllt.
	(VSHLLBQ_N, VSHLLTQ_N): Remove.
	(VSHLLxQ_N): New.
	(VSHLLBQ_M_N, VSHLLTQ_M_N): Remove.
	(VSHLLxQ_M_N): New.
	* config/arm/mve.md (mve_vshllbq_n_<supf><mode>)
	(mve_vshlltq_n_<supf><mode>): Merge into ...
	(@mve_<mve_insn>q_n_<supf><mode>): ... this.
	(mve_vshllbq_m_n_<supf><mode>, mve_vshlltq_m_n_<supf><mode>):
	Merge into ...
	(@mve_<mve_insn>q_m_n_<supf><mode>): ... this.