pinctrl: uniphier: fix register offsets for drive strength control

These pin tables were generated by parsing hardware documents with
a script, but the script had a bug.  Fix the register offsets.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>