fbdev: omapfb: Fix an OF node leak in dss_of_port_get_parent_device()

[ Upstream commit de124b61e179e690277116e6be512e4f422b5dd8 ]

dss_of_port_get_parent_device() leaks an OF node reference when i >= 2
and struct device_node *np is present. Since of_get_next_parent()
obtains a reference of the returned OF node, call of_node_put() before
returning NULL.

This was found by an experimental verifier that I am developing, and no
runtime test was able to be performed due to that lack of actual
devices.

Fixes: f76ee892 ("omapfb: copy omapdss & displays for omapfb")
Signed-off-by: Joe Hattori <joe@pf.is.s.u-tokyo.ac.jp>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>