[APX EGPR] Handle legacy insn that only support GPR16 (1/5)

[APX EGPR] Handle legacy insn that only support GPR16 (1/5)

These legacy insn in opcode map0/1 only support GPR16,
and do not have vex/evex counterpart, directly adjust constraints and
add gpr32 attr to patterns.

insn list:
1. xsave/xsave64, xrstor/xrstor64
2. xsaves/xsaves64, xrstors/xrstors64
3. xsavec/xsavec64
4. xsaveopt/xsaveopt64
5. fxsave64/fxrstor64

gcc/ChangeLog:

	* config/i386/i386.md (<xsave>): Set attr gpr32 0 and constraint
	jm.
	(<xsave>_rex64): Likewise.
	(<xrstor>_rex64): Likewise.
	(<xrstor>64): Likewise.
	(fxsave64): Likewise.
	(fxstore64): Likewise.

gcc/testsuite/ChangeLog:

	* lib/target-supports.exp: Add apxf check.
	* gcc.target/i386/apx-legacy-insn-check-norex2.c: New test.
	* gcc.target/i386/apx-legacy-insn-check-norex2-asm.c: New assembler test.

Co-authored-by: Hongyu Wang <hongyu.wang@intel.com>
Co-authored-by: Hongtao Liu <hongtao.liu@intel.com>