mei: drop unreachable code in mei_start

Device disabled state is caught inside the retry loop, so
there is no need to check it once again afterwards.

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>