hw/arm/smmu-common: smmu base device and datatypes

The patch introduces the smmu base device and class for the ARM
smmu. Devices for specific versions will be derived from this
base device.

We also introduce some important datatypes.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Prem Mallappa <prem.mallappa@broadcom.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1524665762-31355-2-git-send-email-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>