Rework 'state' field usage in per-cpu TSP context

Rework 'state' field usage in per-cpu TSP context

This patch lays the foundation for using the per-cpu 'state' field in
the 'tsp_context' structure for other flags apart from the power state
of the TSP.

It allocates 2 bits for the power state, introduces the necessary
macros to manipulate the power state in the 'state' field and
accordingly reworks all use of the TSP_STATE_* states.

It also allocates a flag bit to determine if the TSP is handling a
standard SMC. If this flag is set then the TSP was interrupted due to
non-secure or EL3 interupt depending upon the chosen routing
model. Macros to get, set and clear this flag have been added as
well. This flag will be used by subsequent patches.

Change-Id: Ic6ee80bd5895812c83b35189cf2c3be70a9024a6