pinctrl: max77620: Use common error handling code in max77620_pinconf_set()

* Add a jump target so that a specific error message is stored only once
  at the end of this function implementation.

* Replace two calls of the function "dev_err" by goto statements.

* Adjust two condition checks.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>