KVM: arm64: selftests: Add init ITS device test

Add some ITS device init tests: general KVM device tests (address not
defined already, address aligned) and tests for the ITS region being
within the addressable IPA range.

Signed-off-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211005011921.437353-12-ricarkol@google.com