iommu/ipmmu-vmsa: Remove all unused register definitions

To support different registers memory mapping hardware easily
in the future, this patch removes all unused register
definitions.

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>