drm: remove redundant minor->device field

Whenever we access minor->device, we are in a minor->kdev->...->fops
callback so the minor->kdev pointer *must* be valid. Thus, simply use
minor->kdev->devt instead of minor->device and remove the redundant field.

Signed-off-by: David Herrmann <[email protected]>
Reviewed-by: Daniel Vetter <[email protected]>

include/drm/drmP.h

@@ -1043,7 +1043,6 @@ struct drm_info_node {
 struct drm_minor {
 	int index;			/**< Minor device number */
 	int type;                       /**< Control or render */
-	dev_t device;			/**< Device number for mknod */
 	struct device *kdev;		/**< Linux device */
 	struct drm_device *dev;