pinctrl: fsl: Make pinctrl_ipc_handle static

Fix sparse warning:

drivers/pinctrl/freescale/pinctrl-scu.c:38:19: warning:
 symbol 'pinctrl_ipc_handle' was not declared. Should it be static?
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/freescale/pinctrl-scu.c

@@ -35,7 +35,7 @@ struct imx_sc_msg_resp_pad_get {
 	u32 val;
 } __packed;
 
-struct imx_sc_ipc *pinctrl_ipc_handle;
+static struct imx_sc_ipc *pinctrl_ipc_handle;
 
 int imx_pinctrl_sc_ipc_init(struct platform_device *pdev)
 {