staging: mt7621-pinctrl: Add of_node_put() before return

staging: mt7621-pinctrl: Add of_node_put() before return

Each iteration of for_each_compatible_node puts the previous node, but
in the case of a return from the middle of the loop, there is no put,
thus causing a memory leak. Add an of_node_put before the return.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Link: https://lore.kernel.org/r/20190716055908.3183-1-nishkadg.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>