gpio/gpio-omap: make platformdata used as *of_device_id.data const

Since of_device_id.data is declared as a pointer to const data a few
more consts can be added in this driver.

Acked-by: Linus Walleij <[e-mail]>
Acked-by: Santosh Shilimkar <[e-mail]>
Signed-off-by: Uwe Kleine-König <[e-mail]>

drivers/gpio/gpio-omap.c

···
 	.fallingdetect =	OMAP4_GPIO_FALLINGDETECT,
 };
 
-static struct omap_gpio_platform_data omap2_pdata = {
+const static struct omap_gpio_platform_data omap2_pdata = {
 	.regs = &omap2_gpio_regs,
 	.bank_width = 32,
 	.dbck_flag = false,
 };
 
-static struct omap_gpio_platform_data omap3_pdata = {
+const static struct omap_gpio_platform_data omap3_pdata = {
 	.regs = &omap2_gpio_regs,
 	.bank_width = 32,
 	.dbck_flag = true,
 };
 
-static struct omap_gpio_platform_data omap4_pdata = {
+const static struct omap_gpio_platform_data omap4_pdata = {
 	.regs = &omap4_gpio_regs,
 	.bank_width = 32,
 	.dbck_flag = true,