perf trace: Add "sendfile64" alias to the "sendfile" syscall

We were looking in tracefs for:

  /sys/kernel/debug/tracing/events/syscalls/sys_enter_sendfile/format when

what is there is just

  /sys/kernel/debug/tracing/events/syscalls/sys_enter_sendfile/format

Its the same id, 40 in x86_64, so just add an alias and let the existing
logic take care of that.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-km2hmg7hru6u4pawi5fi903q@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>