iWRainbowG6: Kill unused file

Change-Id: I7b9b91519d87d70405b57920b3f1ab98c50526d1
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/6810
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>