When the event is passed as list, the default events should be listed as
per 'perf mem record -e list'. Previous behavior is:

  $ perf c2c record -e list
  failed: event 'list' not found, use '-e list' to get list of available events

   Usage: perf c2c record [<options>] [<command>]
      or: perf c2c record [<options>] -- <command> [<options>]

      -e, --event <event>   event selector. Use 'perf mem record -e list' to list available events
  $

New behavior:

  $ perf c2c record -e list
  ldlat-loads  : available
  ldlat-stores : available

v3: is a rebase.
v2: addresses review comments by Jiri Olsa.

https://lore.kernel.org/lkml/20191127081844.GH32367@krava/Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200507220604.3391-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>