perf hist: Count the total cycles of all samples

We can get the per sample cycles by hist__account_cycles(). It's also
useful to know the total cycles of all samples in order to get the
cycles coverage for a single program block in further. For example:

  coverage = per block sampled cycles / total sampled cycles

This patch creates a new argument 'total_cycles' in hist__account_cycles(),
which will be added with the cycles of each sample.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20191107074719.26139-4-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>