staging: mei: adding watchdog ops

adding start and stop function.
start - check if AMT wd client is connected, which is been connected on driver
load.
stop - send stop command to AMT wd.

Signed-off-by: Oren Weil <oren.jer.weil@intel.com>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>