perf tools: Remove nr_sort_keys field

perf tools: Remove nr_sort_keys field

The nr_sort_keys field is to carry the number of sort entries in a
hpp_list or hists to determine the depth of indentation of a hist entry.
As it's only used in hierarchy mode and now we have used nr_hpp_node for
this reason, there's no need to keep it anymore.  Let's get rid of it.

Signed-off-by: Namhyung Kim <[email protected]>
Tested-by: Jiri Olsa <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>