watchdog: move coh901327 state holders

The state holders used in the PM path of the drivers report as
unused variables when compiling without CONFIG_PM so let's
move them inside CONFIG_PM.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>