iommu/vt-d: Don't pre-allocate domain ids for si_domain

There is no reason for this special handling of the
si_domain. The per-iommu domain-id can be allocated
on-demand like for any other domain. So remove the
pre-allocation code.

Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --cc drivers/iommu/intel-iommu.c
Simple merge