canutils: rdep on iproute2

busybox ip fails to configure can interfaces, so we need iproute2 to do so.
See also http://www.armadeus.com/wiki/index.php?title=CAN_bus_Linux_driver

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Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>