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>

drivers/gpu/drm/i915/i915_ioc32.c

@@ -204,7 +204,7 @@ long i915_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	drm_ioctl_compat_t *fn = NULL;
 	int ret;
 
-	if (nr < DRM_COMMAND_BASE)
+	if (nr < DRM_COMMAND_BASE || nr >= DRM_COMMAND_END)
 		return drm_compat_ioctl(filp, cmd, arg);
 
 	if (nr < DRM_COMMAND_BASE + ARRAY_SIZE(i915_compat_ioctls))