aarch64: Add SVE2 faminmax intrinsics

aarch64: Add SVE2 faminmax intrinsics

The AArch64 FEAT_FAMINMAX extension introduces instructions for
computing the floating point absolute maximum and minimum of the
two vectors element-wise.

This patch introduces SVE2 faminmax intrinsics. The intrinsics of this
extension are implemented as the following builtin functions:
* sva[max|min]_[m|x|z]
* sva[max|min]_[f16|f32|f64]_[m|x|z]
* sva[max|min]_n_[f16|f32|f64]_[m|x|z]

gcc/ChangeLog:

	* config/aarch64/aarch64-sve-builtins-base.cc
	(svamax): Absolute maximum declaration.
	(svamin): Absolute minimum declaration.
	* config/aarch64/aarch64-sve-builtins-base.def
	(REQUIRED_EXTENSIONS): Add faminmax intrinsics behind a flag.
	(svamax): Absolute maximum declaration.
	(svamin): Absolute minimum declaration.
	* config/aarch64/aarch64-sve-builtins-base.h: Declaring function
	bases for the new intrinsics.
	* config/aarch64/aarch64.h
	(TARGET_SVE_FAMINMAX): New flag for SVE2 faminmax.
	* config/aarch64/iterators.md: New unspecs, iterators, and attrs
	for the new intrinsics.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/sve2/acle/asm/amax_f16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/amax_f32.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/amax_f64.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/amin_f16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/amin_f32.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/amin_f64.c: New test.