x86: Correct EVEX vector load/store optimization

x86: Correct EVEX vector load/store optimization

Update EVEX vector load/store optimization:

1. There is no need to check AVX since AVX2 is required for AVX512F.
2. We need to check both operands for ZMM register since AT&T syntax
may not set zmmword on the first operand.
3. Update Opcode_SIMD_IntD check and set.
4. Since the VEX prefix has 2 or 3 bytes, the EVEX prefix has 4 bytes,
EVEX Disp8 has 1 byte and VEX Disp32 has 4 bytes, we choose EVEX Disp8
over VEX Disp32.

	* config/tc-i386.c (optimize_encoding): Don't check AVX for
	EVEX vector load/store optimization.  Check both operands for
	ZMM register.  Update EVEX vector load/store opcode check.
	Choose EVEX Disp8 over VEX Disp32.
	* testsuite/gas/i386/optimize-1.d: Updated.
	* testsuite/gas/i386/optimize-1a.d: Likewise.
	* testsuite/gas/i386/optimize-2.d: Likewise.
	* testsuite/gas/i386/optimize-4.d: Likewise.
	* testsuite/gas/i386/optimize-5.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-2.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-2a.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-2b.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-3.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-5.d: Likewise.
	* testsuite/gas/i386/x86-64-optimize-6.d: Likewise.
	* testsuite/gas/i386/optimize-1.s: Add ZMM register load
	test.
	* testsuite/gas/i386/x86-64-optimize-2.s: Likewise.