perf hists browser: Fix typo in function switch_data_file

Should clear buf 'abs_path', not 'options'.

Signed-off-by: Changbin Du <changbin.du@intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 341487ab ("perf hists browser: Add option for runtime switching perf data file")
Link: http://lkml.kernel.org/r/20170313114652.9207-1-changbin.du@intel.com


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