perf callchain: Add generic report parse callchain callback function

This takes the parse_callchain_opt function and copies it into the
callchain.c file.  Now the c2c tool can use it too without duplicating.

Update perf-report to use the new routine too.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1396896924-129847-5-git-send-email-dzickus@redhat.com
[ Adding missing braces to multiline if condition ]
Signed-off-by: Jiri Olsa <jolsa@redhat.com>