ARM: rockchip: fix missing of_node_put calls in smp code

ARM: rockchip: fix missing of_node_put calls in smp code

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

Detected by coccinelle with the following warnings:
./arch/arm/mach-rockchip/pm.c:269:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 259, but without a corresponding object release within this function.
./arch/arm/mach-rockchip/pm.c:275:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 259, but without a corresponding object release within this function
./arch/arm/mach-rockchip/platsmp.c:281:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 272, but without a corresponding object release within this function.
./arch/arm/mach-rockchip/platsmp.c:285:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 272, but without a corresponding object release within this function.
./arch/arm/mach-rockchip/platsmp.c:289:3-9: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 272, but without a corresponding object release within this function.
./arch/arm/mach-rockchip/platsmp.c:303:3-9: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 294, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Suggested-by: Heiko Stuebner <heiko@sntech.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-rockchip@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>