[AArch64] Specify some SVE ACLE functions in a more generic way

[AArch64] Specify some SVE ACLE functions in a more generic way

This patch generalises some boilerplate that becomes much more
common with SVE2 intrinsics.

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

gcc/
	* config/aarch64/aarch64-sve-builtins-functions.h
	(code_for_mode_function): New class.
	(CODE_FOR_MODE0, QUIET_CODE_FOR_MODE0): New macros.
	* config/aarch64/aarch64-sve-builtins-base.cc (svcompact_impl)
	(svext_impl, svmul_lane_impl, svsplice_impl, svtmad_impl): Delete.
	(svcompact, svext, svsplice): Use QUIET_CODE_FOR_MODE0.
	(svmul_lane, svtmad): Use CODE_FOR_MODE0.

From-SVN: r280051