pinctrl: gemini: Fix missing pad descriptions

A pretty clever static checker found a bug in my patch: I added more
bits to a bitmask but didn't extend the array indexed to the same
bitmask.

Fixes: 756a024f ("pinctrl: gemini: Fix GMAC groups")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>