drm: Fix DRM_IOCTL_DEF_DRV()

Currently DRM_IOCTL_DEF_DRV does '[DRM_IOCTL_NR(DRM_##ioctl)]' which
doesn't make much sense since DRM_##ioctl is already a the raw ioctl
number. So change it to 'DRM_IOCTL_NR(DRM_IOCTL_##ioctl) - DRM_COMMAND_BASE'
which means the DRM_IOCTL_NR() now makes sense, and also this also means
if there's a mistake in the DRM_IOCTL_##ioctl macros we might get a
warning about it (eg. we would have gotten a sparse warning about the
i915 colorkey get/set ioctl being defined to be the same thing).
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

include/drm/drmP.h

@@ -263,7 +263,7 @@ struct drm_ioctl_desc {
  */
 
 #define DRM_IOCTL_DEF_DRV(ioctl, _func, _flags)			\
-	[DRM_IOCTL_NR(DRM_##ioctl)] = {.cmd = DRM_##ioctl, .func = _func, .flags = _flags, .cmd_drv = DRM_IOCTL_##ioctl, .name = #ioctl}
+	[DRM_IOCTL_NR(DRM_IOCTL_##ioctl) - DRM_COMMAND_BASE] = {.cmd = DRM_##ioctl, .func = _func, .flags = _flags, .cmd_drv = DRM_IOCTL_##ioctl, .name = #ioctl}
 
 /* Event queued up for userspace to read */
 struct drm_pending_event {