mei: remove unused MEI_IAMTHIF_STALL_TIMER define

MEI_IAMTHIF_STALL_TIMER is unused now and can be safely removed.

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>