superio/ite/*: Factor out generic romstage component

Following the reasoning of:
cf7b498 superio/fintek/*: Factor out generic romstage component

Change-Id: I4c0a9a5a7786eb8fcb0c3ed6251c7fe9bbbadae7
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5585
Tested-by: build bot (Jenkins)
Reviewed-by: Rudolf Marek <r.marek@assembler.cz>