trace: introduce new subsystem

trace: introduce new subsystem

Define the public API for trace support.
This patch also adds support for the build infrastructure and
update the MAINTAINERS file for the trace subsystem.

The 8 bytes tracepoint object is a global variable, and can be used in
fast path. Created a new __rte_trace_point section to store the
tracepoint objects as,
- It is a mostly read-only data and not to mix with other "write"
  global variables.
- Chances that the same subsystem fast path variables come in the same
  fast path cache line. i.e, it will enable a more predictable
  performance number from build to build.

Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
Acked-by: David Marchand <david.marchand@redhat.com>