tracing: add new tracepoints docbook

Add tracepoint docbook. This will help us document and understand
what tracepoints are in the kernel. Since there are multiple
macros, and files that contain tracepoints.

[ Impact: add documentation ]

Signed-off-by: Jason Baron <jbaron@redhat.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: akpm@linux-foundation.org
Cc: rostedt@goodmis.org
Cc: fweisbec@gmail.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: wcohen@redhat.com
LKML-Reference: <84160b6bd94aff02455da7e12bad054d34c579a0.1241107197.git.jbaron@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>