The current method for allocating trace source ID values to sources is
to use a fixed algorithm for CPU based sources of (cpu_num * 2 + 0x10).
The STM is allocated ID 0x1.

This fixed algorithm is used in both the CoreSight driver code, and by
perf when writing the trace metadata in the AUXTRACE_INFO record.

The method needs replacing as currently:-

1. It is inefficient in using available IDs.
2. Does not scale to larger systems with many cores and the algorithm
   has no limits so will generate invalid trace IDs for cpu number > 44.

Additionally requirements to allocate additional system IDs on some
systems have been seen.

This patch set introduces an API that allows the allocation of trace IDs
in a dynamic manner.

Architecturally reserved IDs are never allocated, and the system is
limited to allocating only valid IDs.

Each of the current trace sources ETM3.x, ETM4.x and STM is updated to use
the new API.

For the ETMx.x devices IDs are allocated on certain events
a) When using sysfs, an ID will be allocated on hardware enable, or a read of
sysfs TRCTRACEID register and freed when the sysfs reset is written.

b) When using perf, ID is allocated on during setup AUX event, and freed on
event free. IDs are communicated using the AUX_OUTPUT_HW_ID packet.
The ID allocator is notified when perf sessions start and stop
so CPU based IDs are kept constant throughout any perf session.

Note: This patchset breaks some backward compatibility for perf record and
perf report.

The version of the AUXTRACE_INFO has been updated to reflect the fact that
the trace source IDs are generated differently. This will
mean older versions of perf report cannot decode the newer file.