pinctrl: fix pinconf_pins_show iteration

Commit 706e8520 "pinctrl: correct a offset while enumerating pins"
modified the variable used by pinconf_pin_show()'s for loop, but didn't
update the for loop test expression.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>