platform/chrome: cros_ec: determine `wake_enabled` in cros_ec_suspend()

`wake_enabled` indicates cros_ec_resume() needs to call
disable_irq_wake() to undo enable_irq_wake() in cros_ec_suspend().

Determine `wake_enabled` in cros_ec_suspend() instead of
reset-after-used in cros_ec_resume().

Reviewed-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>