arch-x86: Add byteEnable mask in x86 memhelpers

arch-x86: Add byteEnable mask in x86 memhelpers

Next patch will make the byteEnable mandatory in the ExecContext
interface so we need to amend the existing helpers to make them
use generate the boolean vector.

JIRA: https://gem5.atlassian.net/browse/GEM5-196

Change-Id: Ib24550aa1e22049487ef4ec2748b786be456d342
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23529
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>