x86emul: add memory operand low bits checks for ENQCMD{,S}

x86emul: add memory operand low bits checks for ENQCMD{,S}

Already ISE rev 044 added text to this effect; rev 045 further dropped
leftover earlier text indicating the contrary:
- ENQCMD requires the low 32 bits of the memory operand to be clear,
- ENDCMDS requires bits 20...30 of the memory operand to be clear.

Fixes: d27385968741 ("x86emul: support ENQCMD insns")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>