chg: Unconditionally enable/disable FETs

We used to cache the values.  Now, always set them, because the gas gauge
can change the FETs on its own.

Signed-off-by: Sean Cross <xobs@kosagi.com>
main: Add a delay to power button poweron

Signed-off-by: Sean Cross <xobs@kosagi.com>
power: Persist power state on reboot

Previously, we'd power the mainboard on whenever there was a reboot.
Instead, let's store the power state in a bkp register, and restore
it in case of a watchdog reboot.

Signed-off-by: Sean Cross <xobs@kosagi.com>