video: fbdev: imxfb: Fix missing of_node_put in imxfb_probe

of_parse_phandle returns node pointer with refcount incremented,
use of_node_put() on it when done.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi <lv.ruyi@zte.com.cn>
Signed-off-by: Helge Deller <deller@gmx.de>