perf tools: Explicitly declare inc_group_count as a void function

perf tools: Explicitly declare inc_group_count as a void function

The return type is not defined, so it defaults to int, however, the
function is not returning anything, so this is clearly not correct. Make
it a void function.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1457008214-14393-1-git-send-email-colin.king@canonical.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>