iommu/ipmmu-vmsa: Add utlb_offset_base

iommu/ipmmu-vmsa: Add utlb_offset_base

This is a non-verbatim port of corresponding Linux upsteam commit:
1289f7f15001c7ed36be6d23cb145c1d5feacdc8

Original commit message:
 commit 1289f7f15001c7ed36be6d23cb145c1d5feacdc8
 Author: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
 Date:   Wed Nov 6 11:35:50 2019 +0900

  iommu/ipmmu-vmsa: Add utlb_offset_base

  Since we will have changed memory mapping of the IPMMU in the future,
  this patch adds a utlb_offset_base into struct ipmmu_features
  for IMUCTR and IMUASID registers. No behavior change.

  Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
  Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
  Signed-off-by: Joerg Roedel <jroedel@suse.de>
**********

This is a prereq work needed to add support for S4 series easily
in the future.

Almost the same change as original commit makes, but without updating
struct ipmmu_features_default which Xen driver doesn't have (there is
no support of old Arm32 based Gen2 SoCs).

No change in behavior.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Julien Grall <jgrall@amazon.com>