perf ordered_events: Add ordered_events__flush_time interface

Add OE_FLUSH__TIME flush type, to be able to flush only certain amount
of the queue based on the provided timestamp. It will be used in the
following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Dmitry Levin <ldv@altlinux.org>
Cc: Eugene Syromiatnikov <esyr@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Luis Cláudio Gonçalves <lclaudio@uudg.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20181205160509.1168-7-jolsa@kernel.org


[ Fix the build on older systems such as centos 5 and 6 where 'time' shadows a global declaration ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>