mei: flush queues by the host client only

During queues flush, the me client in most cases is already
unlinked hence the me client id is unavailable. The host client
structure pointer is enough for identification.
The function mei_cl_cmp_id() is dropped as it has no more usage.

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>