Enable perf evlist to use perf.data when it is not owned by current user
or root.

Example:

 # perf record ls
 # chown Yunlong.Song:Yunlong.Song perf.data
 # ls -al perf.data
 -rw------- 1 Yunlong.Song Yunlong.Song 28260 Apr  2 10:18 perf.data
 # id
 uid=0(root) gid=0(root) groups=0(root),64(pkcs11)

Before this patch:

 # perf evlist
 File perf.data not owned by current user or root (use -f to override)
 # perf evlist -f
   Error: unknown switch `f'

  usage: perf evlist [<options>]

     -i, --input <file>    Input file name
     -F, --freq            Show the sample frequency
     -v, --verbose         Show all event attr details
     -g, --group           Show event group information

As shown above, the -f option does not work at all.

After this patch:

 # perf evlist
 File perf.data not owned by current user or root (use -f to override)
 # perf evlist -f
 cycles

As shown above, the -f option really works now.
Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1427982439-27388-2-git-send-email-yunlong.song@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>