drm/xe/migrate: fix offset and len check

drm/xe/migrate: fix offset and len check

Restriction here is pitch of 4bytes to match pixel width (32b), and hw
restriction where src and dst must be aligned to 64bytes. If any of that
is not possible then we need a bounce buffer.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20251022163836.191405-2-matthew.auld@intel.com