drm/i915: Enable command parsing by default

v2: rebased

OTC-Tracker: AXIA-4631
Change-Id: I6747457e1fe7494bd42787af51198fcba398ad78
Signed-off-by: Brad Volkin <bradley.d.volkin@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Resolve tiny conflict in module option text.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>