pinctrl: imx8ulp: Initialize pin_reg

The initialization of pin_reg is missing, causing the following build
warning:

drivers/pinctrl/freescale/pinctrl-imx8ulp.c:228:35: warning: 'pin_reg' is used uninitialized in this function [-Wuninitialized]

Initialize pin_reg the same way as it is done on vf610 and imx7ulp
to fix the problem.

Fixes: 16b343e8 ("pinctrl: imx8ulp: Add pinctrl driver support")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20210723203242.88845-1-festevam@gmail.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/freescale/pinctrl-imx8ulp.c

@@ -225,6 +225,10 @@ static int imx8ulp_pmx_gpio_set_direction(struct pinctrl_dev *pctldev,
 	const struct imx_pin_reg *pin_reg;
 	u32 reg;
 
+	pin_reg = &ipctl->pin_regs[offset];
+	if (pin_reg->mux_reg == -1)
+		return -EINVAL;
+
 	reg = readl(ipctl->base + pin_reg->mux_reg);
 	if (input)
 		reg = (reg & ~BM_OBE_ENABLED) | BM_IBE_ENABLED;