AArch64: Add support for SIMD xor immediate (3/3)

Add support for SVE xor immediate when generating AdvSIMD code and SVE is
available.

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (enum simd_immediate_check): Add
	AARCH64_CHECK_XOR.
	(aarch64_simd_valid_xor_imm): New function.
	(aarch64_output_simd_imm): Add AARCH64_CHECK_XOR support.
	(aarch64_output_simd_xor_imm): New function.
	* config/aarch64/aarch64-protos.h (aarch64_output_simd_xor_imm): New
	prototype.
	(aarch64_simd_valid_xor_imm): New prototype.
	* config/aarch64/aarch64-simd.md (xor<mode>3<vczle><vczbe>):
	Use aarch64_reg_or_xor_imm predicate and add an immediate alternative.
	* config/aarch64/predicates.md (aarch64_reg_or_xor_imm): Add new
	predicate.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/sve/simd_imm.c: New test.