drivers/video/via/via-gpio.c: fix warning

drivers/video/via/via-gpio.c: In function 'viafb_gpio_probe':
drivers/video/via/via-gpio.c:216: warning: assignment from incompatible pointer type

Cc: Joseph Chan <[e-mail]>
Cc: Scott Fang <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Florian Tobias Schandinat <[e-mail]>

drivers/video/via/via-gpio.c

···
 	struct gpio_chip gpio_chip;
 	struct viafb_dev *vdev;
 	struct viafb_gpio *active_gpios[VIAFB_NUM_GPIOS];
-	char *gpio_names[VIAFB_NUM_GPIOS];
+	const char *gpio_names[VIAFB_NUM_GPIOS];
 };
 
 /*