mei: wd: use watchdog_set/get_drvdata for passing mei_device

use watchdog_set/get_drvdata for passing mei_device
to watchdog_ops handlers instead of using global mei_device

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