perf tools: Refactor the code to strip command name with {l,r}trim()

After reading command name from /proc/<pid>/status, use ltrim() and
rtrim() to strip command name, not using just while loop, isspace() and
etc.

Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Acked-by: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1491575061-704-6-git-send-email-treeze.taeung@gmail.com


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