ANDROID: KVM: arm64: iommu: Remove iommu from alloc_domain

Remove iommu from alloc_domain which is the last domain function
that still uses iommu in args.
This completely decouples the interfaces of the IOMMU HVCs and
drivers.

However, domain still has an IOMMU pointer, this is fixed next.

As the SMMU driver, can't allocate a page table until it knows the
SMMU properties, this is postponed to attach_dev in a finalize
function.

Bug: 277989609
Bug: 278749606
Change-Id: Ie1eeb8b8747535beaa59ddfe829cf6cf4016bd77
Signed-off-by: Mostafa Saleh <smostafa@google.com>