pinctrl: samsung: Remove hardcoded register offsets

This patch replaces statically hardcoded register offsets of Exynos SoCs
with an array of register offsets in samsung_pin_bank_type struct.

Thanks to this change, support for SoCs with other set and order of
registers can be added (e.g. S3C24xx and S3C64xx).

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