gpio: staticize xway_stp_init()

This initcall is only called from the driver itself, staticize it.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpio-stp-xway.c b/drivers/gpio/gpio-stp-xway.c
index 04882a9..7e359b7 100644
--- a/drivers/gpio/gpio-stp-xway.c
+++ b/drivers/gpio/gpio-stp-xway.c
@@ -292,7 +292,7 @@
 	},
 };
 
-int __init xway_stp_init(void)
+static int __init xway_stp_init(void)
 {
 	return platform_driver_register(&xway_stp_driver);
 }