perf trace: Beautify flock 'cmd' arg

perf trace: Beautify flock 'cmd' arg

  4735.638 ( 0.003 ms): man/19881 flock(fd: 3, cmd: SH|NB) = 0
  4735.832 ( 0.002 ms): man/19881 flock(fd: 3, cmd: UN   ) = 0

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-amh3y88kh1nmclpwezqlarl8@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>