drm/xe: Make page-table updates using the default engine happen in order

If the default engine m->eng was used, there is no check for idle and
a cpu page-table update may thus happen in parallel with a gpu one.
Don't allow CPU page-table updates with the default engine until
the engine is idle.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230629205134.111849-2-thomas.hellstrom@linux.intel.com


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>