fbdev: omapfb: Call of_node_put(ep) only once in omapdss_of_find_source_for_first_ep()

An of_node_put(ep) call was immediately used after a pointer check
for a of_graph_get_remote_port() call in this function implementation.
Thus call such a function only once instead directly before the check.

This issue was transformed by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Helge Deller <deller@gmx.de>