[AArch64] Pass a mode to some SVE immediate queries

[AArch64] Pass a mode to some SVE immediate queries

It helps the SVE2 ACLE support if aarch64_sve_arith_immediate_p and
aarch64_sve_sqadd_sqsub_immediate_p accept scalars as well as vectors.

2020-01-09  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64-protos.h (aarch64_sve_arith_immediate_p)
	(aarch64_sve_sqadd_sqsub_immediate_p): Add a machine_mode argument.
	* config/aarch64/aarch64.c (aarch64_sve_arith_immediate_p)
	(aarch64_sve_sqadd_sqsub_immediate_p): Likewise.  Handle scalar
	immediates as well as vector ones.
	* config/aarch64/predicates.md (aarch64_sve_arith_immediate)
	(aarch64_sve_sub_arith_immediate, aarch64_sve_qadd_immediate)
	(aarch64_sve_qsub_immediate): Update calls accordingly.

From-SVN: r280059