libtx2bpmp: Use device tree for addresses

Extract MMIO addresses from the provided device tree. Also use
PS_DRIVER_MODULE_DEFINE for registering the tx2_bpmp driver as a driver
with the framework for initialization.

libtx2bpmp: Change HSP public interface

Following from the previous BPMP interface commit, this also changes the
HSP interface so that it makes it easier to integrate with the interface
registration service.

libtx2bpmp: Add drivers for the TX2 HSP mechanisms

The HSP mechanisms are used by the BPMP driver to allow the main
processor to synchronise with the BPMP co-processor.