gpio: Add missing spin_lock_init in gpio-pch driver

This bug was introduced by commit d568a681
"gpio-pch: add spinlock in suspend/resume processing"
which adds a spinlock to struct pch_gpio but never init the spinlock.

Reported-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>