AVX512FP16: Support basic 64/32bit vector type and operation.

AVX512FP16: Support basic 64/32bit vector type and operation.

For 32bit target, V4HF vector is parsed same as __m64 type, V2HF
is parsed by stack and returned from GPR since it is not specified
by ABI.

gcc/ChangeLog:

	PR target/102230
	* config/i386/i386.h (VALID_AVX512FP16_REG_MODE): Add
	V2HF mode check.
	(VALID_SSE2_REG_VHF_MODE): Add V4HFmode and V2HFmode.
	(VALID_MMX_REG_MODE): Add V4HFmode.
	(SSE_REG_MODE_P): Replace VALID_AVX512FP16_REG_MODE with
	vector mode condition.
	* config/i386/i386.c (classify_argument): Parse V4HF/V2HF
	via sse regs.
	(function_arg_32): Add V4HFmode.
	(function_arg_advance_32): Likewise.
	* config/i386/i386.md (mode): Add V4HF/V2HF.
	(MODE_SIZE): Likewise.
	* config/i386/mmx.md (MMXMODE): Add V4HF mode.
	(V_32): Add V2HF mode.
	(VHF_32_64): New mode iterator.
	(*mov<mode>_internal): Adjust sse alternatives to support
	V4HF mode move.
	(*mov<mode>_internal): Adjust sse alternatives to support
	V2HF mode move.
	(<insn><mode>3): New define_insn for add/sub/mul/div.

gcc/testsuite/ChangeLog:

	PR target/102230
	* gcc.target/i386/avx512fp16-floatvnhf.c: Remove xfail.
	* gcc.target/i386/avx512fp16-trunc-extendvnhf.c: Ditto.
	* gcc.target/i386/avx512fp16-truncvnhf.c: Ditto.
	* gcc.target/i386/avx512fp16-64-32-vecop-1.c: New test.
	* gcc.target/i386/avx512fp16-64-32-vecop-2.c: Ditto.
	* gcc.target/i386/pr102230.c: Ditto.