staging: mei: mei_dev - kill unused members

remove write only/unsed variables
mei_dev.write_hang and mei_io_lis.tdevice_extension

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Oren Weil <oren.jer.weil@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>