media: camss: Fix OF node usage

of_graph_get_next_endpoint increases the refcount of the returned
node and decreases the refcount of the passed node. Take this into
account and use of_node_put properly.

Signed-off-by: Todor Tomov <todor.tomov@linaro.org>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>