media: mtk-mdp: Fix a refcounting bug on error in init

We need to call of_node_put(comp->dev_node); on the error paths in this
function.

Fixes: c8eb2d7e ("[media] media: Add Mediatek MDP Driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>