gpio-pch: modify gpio_nums and mask

Currently, the number of GPIO pins is set fixed value(=12).
Also PIN MASK is set as '0xfff'.
However the pins differs by IOH.
This patch sets the value correctly.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>