drm: sti: fix device leaks at component probe

drm: sti: fix device leaks at component probe

Make sure to drop the references taken to the vtg devices by
of_find_device_by_node() when looking up their driver data during
component probe.

Note that holding a reference to a platform device does not prevent its
driver data from going away so there is no point in keeping the
reference after the lookup helper returns.

Fixes: cc6b741c6f63 ("drm: sti: remove useless fields from vtg structure")
Cc: stable@vger.kernel.org	# 4.16
Cc: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20250922122012.27407-1-johan@kernel.org
Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>