drm/udl: Remove unused field gem_lock from struct udl_device

Reduce the size of struct udl_device by removing the unused
field gem_lock.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Patrik Jakobsson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/udl/udl_drv.h

···
 	struct drm_encoder encoder;
 	struct drm_connector connector;
 
-	struct mutex gem_lock;
-
 	int sku_pixel_limit;
 
 	struct urb_list urbs;

drivers/gpu/drm/udl/udl_main.c

···
 		drm_warn(dev, "buffer sharing not supported"); /* not an error */
 	}
 
-	mutex_init(&udl->gem_lock);
-
 	if (!udl_parse_vendor_descriptor(udl)) {
 		ret = -ENODEV;
 		DRM_ERROR("firmware not recognized. Assume incompatible device\n");