mei: mei_hbm_dispatch() returns void

mei: mei_hbm_dispatch() returns void

Building hbm.o for v3.13.2 triggers a GCC warning:
    drivers/misc/mei/hbm.c: In function 'mei_hbm_dispatch':
    drivers/misc/mei/hbm.c:596:3: warning: 'return' with a value, in function returning void [enabled by default]
       return 0;
       ^

GCC is correct, obviously. So let's return void instead of zero here.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Cc: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>