Revert "powerpc/pseries/iommu: Fix iommu initialisation during DLPAR add"

This reverts commit ed8b94f6

.

Gaurav reported that there are still problems with the patch and it
should be reverted pending a fuller fix.

Link: https://lore.kernel.org/all/4f6fc1ac-7a76-4447-9d0e-f55c0be373f8@linux.ibm.com/
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>