perf timechart: Support using -f to override perf.data file ownership

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

Example:

 # perf timechart record ls
 # chown Yunlong.Song:Yunlong.Song perf.data
 # ls -al perf.data
 -rw------- 1 Yunlong.Song Yunlong.Song 5471744 Apr  2 15:15 perf.data
 # id
 uid=0(root) gid=0(root) groups=0(root),64(pkcs11)

Before this patch:

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

  usage: perf timechart [<options>] {record}

     -i, --input <file>    input file name
     -o, --output <file>   output file name
     -w, --width <n>       page width
         --highlight <duration or task name>
                           highlight tasks. Pass duration in ns or process name.
     -P, --power-only      output power data only
     -T, --tasks-only      output processes data only
     -p, --process <process>
                           process selector. Pass a pid or process name.
         --symfs <directory>
                           Look for files with symbols relative to this directory
     -n, --proc-num <n>    min. number of tasks to print
     -t, --topology        sort CPUs according to topology
         --io-skip-eagain  skip EAGAIN errors
         --io-min-time <time>
                           all IO faster than min-time will visually appear longer
         --io-merge-dist <time>
                           merge events that are merge-dist us apart

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

After this patch:

 # perf timechart
 File perf.data not owned by current user or root (use -f to override)
 # perf timechart -f
 Written 0.0 seconds of trace to output.svg.
 # cat output.svg
 <?xml version="1.0" standalone="no"?>
 <!DOCTYPE svg SYSTEM "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
 <svg width="1000" height="10110" version="1.1" xmlns="http://www.w3.org/2000/svg

">
 <defs>
   <style type="text/css">
     <![CDATA[
       rect          { stroke-width: 1; }
 ...
 ...

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/1427982439-27388-9-git-send-email-yunlong.song@huawei.com


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