perf trace: Add beautifier for lseek's whence arg

 [root@zoo ~]# perf trace -a -e lseek | head -1
    546.922 ( 0.004 ms): 1184 lseek(fd: 26, offset: 0, whence: CUR) = 2
 [root@zoo ~]#

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-2eiuhwz9jbnhj80q6jaqeji4@git.kernel.org


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