The K3 family of SoCs has multiple interconnects. The key interconnect
for high performance processors is the MSMC3 interconnect. This is
an io-coherent interconnect which exports multiple ports for each
processor cluster.

Sometimes, port 0 of the MSMC may not have an ARM cluster OR is isolated
such that the instance of ATF does not manage it. Define macros
in platform_def.h to help handle this.

Signed-off-by: Benjamin Fair <b-fair@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Andrew F. Davis <afd@ti.com>