mei: fix memory leak of mei_clients array

we never freed the mei_clients array on driver shutdown
only on reset
add mei_hbm_reset function that wraps the hbm cleanup

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