gpu: ipu-v3: pre: fix device node leak in ipu_pre_lookup_by_phandle

Before returning, call of_node_put() for the device node returned by
of_parse_phandle().

Fixes: d2a34232

 ("gpu: ipu-v3: add driver for Prefetch Resolve Engine")
Signed-off-by: Tobias Jordan <Tobias.Jordan@elektrobit.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>