pinctrl: cy8c95x0: Lock register accesses in cy8c95x0_set_mux()

It seems that cy8c95x0_set_mux() missed serialization of IO access.
And its implementation looks half-baked. Add locking to the function.

Fixes: e6cbbe42 ("pinctrl: Add Cypress cy8c95x0 support")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220916205450.86278-1-andriy.shevchenko@linux.intel.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-cy8c95x0.c

@@ -1152,8 +1152,13 @@ static int cy8c95x0_set_mux(struct pinctrl_dev *pctldev, unsigned int selector,
 			    unsigned int group)
 {
 	struct cy8c95x0_pinctrl *chip = pinctrl_dev_get_drvdata(pctldev);
+	int ret;
 
-	return cy8c95x0_pinmux_cfg(chip, selector, group);
+	mutex_lock(&chip->i2c_lock);
+	ret = cy8c95x0_pinmux_cfg(chip, selector, group);
+	mutex_unlock(&chip->i2c_lock);
+
+	return ret;
 }
 
 static const struct pinmux_ops cy8c95x0_pmxops = {