perf tools: Change (symbol|annotation)__calc_percent return type to void

There's no need for symbol__calc_percent and annotation__calc_percent
functions to return any value, since it's always zero. Changing both
function to return void.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-z0gs28hh24m4gia1t1ctraye@git.kernel.org


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