gpu/drm: clean up white space in drm_legacy_lock_master_cleanup()

We moved this code to a different file and accidentally deleted a
newline.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200108054312.yzlj5wmbdktejgob@kili.mountain