Don't wait for GPU to be able to update page-tables using CPU. Putting
ourselves to sleep may be more of a problem than using GPU for
page-table updates. Also allow the vm to be NULL since the migrate
kunit test uses NULL for vm.
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Reviewed-by: Matthew Auld <matthew.auld@intel.com> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>