pinctrl: samsung: Handle banks with two configuration registers

This patch adds support for banks that have more than one function
configuration registers, e.g. some of the banks of S3C64xx SoCs.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>