mei: bus: call mei_cl_read_start under device lock

Ensure that mei_cl_read_start is called under the device lock
also in the bus layer. The function updates global ctrl_wr_list
which should be locked.

Cc: <stable@vger.kernel.org> #4.4+
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>