pinctrl: rockchip: constify rockchip_pin_ctrl for RK3036

There's no need to modify private data from the controller, so let's
make that struct const.

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/drivers/pinctrl/rockchip/pinctrl-rk3036.c b/drivers/pinctrl/rockchip/pinctrl-rk3036.c
index b14386c..8d0c0e0 100644
--- a/drivers/pinctrl/rockchip/pinctrl-rk3036.c
+++ b/drivers/pinctrl/rockchip/pinctrl-rk3036.c
@@ -80,7 +80,7 @@
 	PIN_BANK(2, 32, "gpio2"),
 };
 
-static struct rockchip_pin_ctrl rk3036_pin_ctrl = {
+static const struct rockchip_pin_ctrl rk3036_pin_ctrl = {
 	.pin_banks		= rk3036_pin_banks,
 	.nr_banks		= ARRAY_SIZE(rk3036_pin_banks),
 	.grf_mux_offset		= 0xa8,