x86: Support Intel AVX VNNI

Intel AVX VNNI instructions are marked with CpuVEX_PREFIX.  Without the
pseudo {vex} prefix, mnemonics of Intel VNNI instructions are encoded
with the EVEX prefix.  The pseudo {vex} prefix can be used to encode
mnemonics of Intel VNNI instructions with the VEX prefix.

gas/

	* NEWS: Add Intel AVX VNNI.
	* config/tc-i386.c (cpu_arch): Add .avx_vnni and noavx_vnni.
	(cpu_flags_match): Support CpuVEX_PREFIX.
	* doc/c-i386.texi: Document .avx_vnni, noavx_vnni and how to
	encode Intel VNNI instructions with VEX prefix.
	* testsuite/gas/i386/avx-vnni.d: New file.
	* testsuite/gas/i386/avx-vnni.s: Likewise.
	* testsuite/gas/i386/x86-64-avx-vnni.d: Likewise.
	* testsuite/gas/i386/x86-64-avx-vnni.s: Likewise.
	* testsuite/gas/i386/i386.exp: Run AVX VNNI tests.

opcodes/

	* i386-dis.c (PREFIX_VEX_0F3850): New.
	(PREFIX_VEX_0F3851): Likewise.
	(PREFIX_VEX_0F3852): Likewise.
	(PREFIX_VEX_0F3853): Likewise.
	(VEX_W_0F3850_P_2): Likewise.
	(VEX_W_0F3851_P_2): Likewise.
	(VEX_W_0F3852_P_2): Likewise.
	(VEX_W_0F3853_P_2): Likewise.
	(prefix_table): Add PREFIX_VEX_0F3850, PREFIX_VEX_0F3851,
	PREFIX_VEX_0F3852 and PREFIX_VEX_0F3853.
	(vex_table): Add VEX_W_0F3850_P_2, VEX_W_0F3851_P_2,
	VEX_W_0F3852_P_2 and VEX_W_0F3853_P_2.
	(putop): Add support for "XV" to print "{vex3}" pseudo prefix.
	* i386-gen.c (cpu_flag_init): Clear the CpuAVX_VNNI bit in
	CPU_UNKNOWN_FLAGS.  Add CPU_AVX_VNNI_FLAGS and
	CPU_ANY_AVX_VNNI_FLAGS.
	(cpu_flags): Add CpuAVX_VNNI and CpuVEX_PREFIX.
	* i386-opc.h (CpuAVX_VNNI): New.
	(CpuVEX_PREFIX): Likewise.
	(i386_cpu_flags): Add cpuavx_vnni and cpuvex_prefix.
	* i386-opc.tbl: Add Intel AVX VNNI instructions.
	* i386-init.h: Regenerated.
	* i386-tbl.h: Likewise.