include/trace/events/vmscan.h: drop zone id from kswapd tracepoints

include/trace/events/vmscan.h: drop zone id from kswapd tracepoints

It is not clear how the zone id is useful in kswapd tracepoints and the id
itself is not really easy to process because it depends on the
configuration (available zones).  Let's drop the id for now.  If somebody
really needs that information then the zone name should be used instead.

[mhocko@suse.com: new changelog]
Link: http://lkml.kernel.org/r/1552451813-10833-1-git-send-email-laoar.shao@gmail.com
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>