perf evlist: Introduce control file descriptors

perf evlist: Introduce control file descriptors

Define and initialize control file descriptors.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/0dd4f544-2610-96d6-1bdb-6582bdc3dc2c@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>