drm/i915/selftest: use igt_vma_move_to_active_unlocked if possible

Helper replaces common sequence of calls.

Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221213121951.1515023-2-andrzej.hajda@intel.com