pinctrl: aspeed: Fix potential NULL dereference in aspeed_pinmux_set_mux()

pdesc could be null but still dereference pdesc->name and it will lead to
a null pointer access. So we move a null check before dereference.

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Link: https://lore.kernel.org/r/1650508019-22554-1-git-send-email-baihaowen@meizu.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: Lotte-Bai

drivers/pinctrl/aspeed/pinctrl-aspeed.c

@@ -236,11 +236,11 @@ int aspeed_pinmux_set_mux(struct pinctrl_dev *pctldev, unsigned int function,
 		const struct aspeed_sig_expr **funcs;
 		const struct aspeed_sig_expr ***prios;
 
-		pr_debug("Muxing pin %s for %s\n", pdesc->name, pfunc->name);
-
 		if (!pdesc)
 			return -EINVAL;
 
+		pr_debug("Muxing pin %s for %s\n", pdesc->name, pfunc->name);
+
 		prios = pdesc->prios;
 
 		if (!prios)