dt-bindings: pinctrl: fix spelling mistakes in pinctl documentation

The spelling of configured is incorrect in the documentation. Fix it.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>