perf/bpf: Extend the perf_event_read_local() interface, a.k.a. "bpf: perf event change needed for subsequent bpf helpers"

eBPF programs would like access to the (perf) event enabled and
running times along with the event value, such that they can deal with
event multiplexing (among other things).

This patch extends the interface; a future eBPF patch will utilize
the new functionality.

[ Note, there's a same-content commit with a poor changelog and a meaningless
  title in the networking tree as well - but we need this change for subsequent
  perf work, so apply it here as well, with a proper changelog. Hopefully Git
  will be able to sort out this somewhat messy workflow, if there are no other,
  conflicting changes to these files. ]
Signed-off-by: NYonghong Song <yhs@fb.com>
[ Rewrote the changelog. ]
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <ast@fb.com>
Cc: <daniel@iogearbox.net>
Cc: <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David S. Miller <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20171005161923.332790-2-yhs@fb.comSigned-off-by: NIngo Molnar <mingo@kernel.org>