ANDROID: KVM: arm64: iommu: Register IOMMU driver dynamically

As step to modularize the driver, make IOMMU registration dynamic.
Remove static calls to the SMMUv3 driver, and remove the IOMMU driver
from pkvm_init HVC.

Add a new file for IOMMU EL1 functions.

Bug: 277989609
Bug: 278749606
Change-Id: Ie742f12c2307248f77e85af9480c4745e188ebb9
Signed-off-by: Mostafa Saleh <smostafa@google.com>