drm/i915: Forward all core DRM ioctls to core compat handling

Previously only core DRM ioctls under the DRM_COMMAND_BASE were being
forwarded, but the drm.h header suggests (and reality confirms) ones
after (and including) DRM_COMMAND_END should be forwarded as well.

We need this to correctly forward the compat ioctl for the botched-up
addfb2.1 extension.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: stable@vger.kernel.org # 4.1+
[danvet: Explain why this is suddenly needed and add cc: stable.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>