drm: rcar-du: fix incorrect return in rcar_du_crtc_cleanup()

drm: rcar-du: fix incorrect return in rcar_du_crtc_cleanup()

The rcar_du_crtc_cleanup() function has a void return type, but
incorrectly uses a return statement with a call to drm_crtc_cleanup(),
which also returns void.

Remove the return statement to ensure proper function semantics.
No functional change intended.

Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Link: https://patch.msgid.link/20251017191634.1454201-1-alok.a.tiwari@oracle.com
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>