media: mtk-vcodec: Release device nodes in mtk_vcodec_init_enc_pm()

of_parse_phandle() returns the device node with refcount incremented.
There are two nodes that are used temporary in mtk_vcodec_init_enc_pm(),
but their refcounts are not decremented.

The patch adds one of_node_put() and fixes returning error codes.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>