pinctrl: uniphier: fix pin_config_get() for input-enable

For LD11/LD20 SoCs (capable of per-pin input enable), iectrl bits are
located across multiple registers.  So, the register offset must be
taken into account.  Otherwise, wrong input-enable status is displayed.

While we here, rename the macro because it is a base address.

Fixes: aa543888 ("pinctrl: uniphier: support per-pin input enable for new SoCs")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>