drm: fix tainted kernel caused by drm_panel_orientation_quirks.c

drm_panel_orientation_quirks.c introduced in commit 404d1a3e ("drm:
Add panel orientation quirks, v6.") taints the kernel when compiled as a
module. Fix this by adding MODULE_LICENSE().

Signed-off-by: David Lechner <david@lechnology.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1513881979-13801-1-git-send-email-david@lechnology.com