Input: synaptics-rmi4 - do not check for NULL when calling of_node_put()

The of_node_put() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>