[PATCH] ibmveth: Remove ibmveth "liobn" field

Remove the now unused "liobn" field in ibmveth which also avoids
having insider knowledge of the iommu table in that driver.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Santiago Leon <santil@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>