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

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 <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>