perf stat: Remove a set of shadow stats static variables

In previous patches, we have reconstructed the code and let it not
access the static variables directly.

This patch removes these static variables.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1512482591-4646-7-git-send-email-yao.jin@linux.intel.com


[ Rename 'stat' variables to 'st' to build on centos:{5,6} and others where it shadows a global declaration ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>