pinctrl: airoha: fix pinctrl function mismatch issue

pinctrl: airoha: fix pinctrl function mismatch issue

The blamed commit made the following changes:

-#define PINCTRL_FUNC_DESC(id)...
-		.desc = PINCTRL_PINFUNCTION(#id, ...
+#define PINCTRL_FUNC_DESC(id, table)...
+		.desc = PINCTRL_PINFUNCTION(#id, ...

-	PINCTRL_FUNC_DESC(pon)...
+	PINCTRL_FUNC_DESC("pon", pon)...

It's clear that the id of funcs doesn't match the definition.
Remove redundant #string from the definition to fix this issue:
pinctrl-airoha ...: invalid function mdio in map table

Fixes: 4043b0c45f85 ("pinctrl: airoha: generalize pins/group/function/confs handling")
Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Acked-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>