mei: move amthif specific release code to amithif

Move amthif code part into separate function
mei_amthif_release.
Also helper functions mei_clear_list and mei_clear_lists
are moved along

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