x86: Clear modrm if not needed

x86: Clear modrm if not needed

The MODRM byte can be checked to display the instruction name only if the
MODRM byte needed.  Clear modrm if the MODRM byte isn't needed so that
modrm field checks in putop like, modrm.mod == N with N != 0, can be done
without checking need_modrm.

gas/

	PR binutils/26705
	* testsuite/gas/i386/x86-64-suffix.s: Add "mov %rsp,%rbp" before
	sysretq.
	* testsuite/gas/i386/x86-64-suffix-intel.d: Updated.
	* testsuite/gas/i386/x86-64-suffix.d: Likewise.

opcodes/

	PR binutils/26705
	* i386-dis.c (print_insn): Clear modrm if not needed.
	(putop): Check need_modrm for modrm.mod != 3.  Don't check
	need_modrm for modrm.mod == 3.