mainboard/ibase/mb899: Sanitize headers

These are not local headers.

Change-Id: Ie0b0a682565a08dbfa089986dc7860fdb0846949
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5796
Tested-by: build bot (Jenkins)
Reviewed-by: Idwer Vollering <vidwer@gmail.com>