pinctrl: rzg2l: Variable may not have been assigned to

pinctrl: rzg2l: Variable may not have been assigned to

In rzg2l_pinconf_set and rzg2l_get_pin_muxing if the call to
rzg2l_selector_decode fails then the variable pin may not have been
assigned to. Remove the use of pin from the error message. Also update
the error message to show the invalid selector used instead of port
which will be the error code returned.

This issue was found by Smatch.

Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
Reviewed-by: Paul Barker <paul@pbarker.dev>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>