MIPS: AR7: constify some arrays in gpio and prom code

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2980/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/ar7/gpio.c b/arch/mips/ar7/gpio.c
index bb571bc..d8dbd8f 100644
--- a/arch/mips/ar7/gpio.c
+++ b/arch/mips/ar7/gpio.c
@@ -217,7 +217,7 @@
 	u32 func;
 };
 
-static struct titan_gpio_cfg titan_gpio_table[] = {
+static const struct titan_gpio_cfg titan_gpio_table[] = {
 	/* reg, start bit, mux value */
 	{4, 24, 1},
 	{4, 26, 1},