pinctrl: zte: fix leaked of_node references

pinctrl: zte: fix leaked of_node references

The call to of_parse_phandle returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.

Detected by coccinelle with the following warnings:
./drivers/pinctrl/zte/pinctrl-zx.c:415:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 407, but without a corresponding object release within this function.
./drivers/pinctrl/zte/pinctrl-zx.c:422:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 407, but without a corresponding object release within this function.
./drivers/pinctrl/zte/pinctrl-zx.c:436:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 407, but without a corresponding object release within this function.
./drivers/pinctrl/zte/pinctrl-zx.c:444:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 407, but without a corresponding object release within this function.
./drivers/pinctrl/zte/pinctrl-zx.c:448:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 407, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Jun Nie <jun.nie@linaro.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-gpio@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>