mei: wd: decouple and revamp watchdog state machine

Before ME watchdog was exported through standard watchdog interface
it was closed and started together with the mei device.

The major issue is that closing ME watchdog disabled also MEI device,
to fix this the watchdog state machine has to be independent from MEI
state machine.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>