perf srcline: Fix memory leak in addr2inlines()

perf srcline: Fix memory leak in addr2inlines()

When libbfd is not used, addr2inlines() executes `addr2line -i` and
process output line by line.  But it resets filename to NULL in the loop
so getline() allocates additional memory everytime instead of realloc.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20171031020654.31163-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>