We have used callchain_node->hit to measure the hot level of one stream.
This patch calculates the sum of hits of total streams.

Thus in next patch, we can use following formula to report hot percent
for one stream.

hot percent = callchain_node->hit / sum of total hits
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20201009022845.13141-6-yao.jin@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>