drm: Kill user_modes list and the associated ioctls

There is no way to use modes added to the user_modes list. We never
look at the contents of said list in the kernel, and the only operations
userspace can do are attach and detach. So the only "benefit" of this
interface is wasting kernel memory.

Fortunately it seems no real user space application ever used these
ioctls. So just kill them.

Also remove the prototypes for the non-existing drm_mode_addmode_ioctl()
and drm_mode_rmmode_ioctl() functions.

v2: Use drm_noop instead of completely removing the ioctls

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 73a99e4..5a57be6 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -711,8 +711,8 @@
 #define DRM_IOCTL_MODE_SETGAMMA		DRM_IOWR(0xA5, struct drm_mode_crtc_lut)
 #define DRM_IOCTL_MODE_GETENCODER	DRM_IOWR(0xA6, struct drm_mode_get_encoder)
 #define DRM_IOCTL_MODE_GETCONNECTOR	DRM_IOWR(0xA7, struct drm_mode_get_connector)
-#define DRM_IOCTL_MODE_ATTACHMODE	DRM_IOWR(0xA8, struct drm_mode_mode_cmd)
-#define DRM_IOCTL_MODE_DETACHMODE	DRM_IOWR(0xA9, struct drm_mode_mode_cmd)
+#define DRM_IOCTL_MODE_ATTACHMODE	DRM_IOWR(0xA8, struct drm_mode_mode_cmd) /* deprecated (never worked) */
+#define DRM_IOCTL_MODE_DETACHMODE	DRM_IOWR(0xA9, struct drm_mode_mode_cmd) /* deprecated (never worked) */
 
 #define DRM_IOCTL_MODE_GETPROPERTY	DRM_IOWR(0xAA, struct drm_mode_get_property)
 #define DRM_IOCTL_MODE_SETPROPERTY	DRM_IOWR(0xAB, struct drm_mode_connector_set_property)