rockchip: Convert the PMU IOMUX registers into an array

This is easier to deal with when using generic code since it allows us to
use a register index instead of naming each register.

Adjust it, adding an enum to improve readability.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pinctrl/rockchip/pinctrl_rk3288.c b/drivers/pinctrl/rockchip/pinctrl_rk3288.c
index c432a00..ec3c4fe 100644
--- a/drivers/pinctrl/rockchip/pinctrl_rk3288.c
+++ b/drivers/pinctrl/rockchip/pinctrl_rk3288.c
@@ -56,10 +56,10 @@
 {
 	switch (i2c_id) {
 	case PERIPH_ID_I2C0:
-		clrsetbits_le32(&pmu->gpio0b_iomux,
+		clrsetbits_le32(&pmu->gpio0_iomux[PMU_GPIO0_B],
 				GPIO0_B7_MASK << GPIO0_B7_SHIFT,
 				GPIO0_B7_I2C0PMU_SDA << GPIO0_B7_SHIFT);
-		clrsetbits_le32(&pmu->gpio0b_iomux,
+		clrsetbits_le32(&pmu->gpio0_iomux[PMU_GPIO0_C],
 				GPIO0_C0_MASK << GPIO0_C0_SHIFT,
 				GPIO0_C0_I2C0PMU_SCL << GPIO0_C0_SHIFT);
 		break;