mei: start disconnect request timer consistently

Link must be reset in case the fw doesn't
respond to client disconnect request.
We did charge the timer only in irq path
from mei_cl_irq_close and not in mei_cl_disconnect

Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>