ring-buffer: Incorporate absolute timestamp into add_timestamp logic

Instead of calling out the absolute test for each time to check if the
ring buffer wants absolute time stamps for all its recording, incorporate it
with the add_timestamp field and turn it into flags for faster processing
between wanting a absolute tag and needing to force one.

Link: http://lkml.kernel.org/r/20200629025259.154892368@goodmis.org



Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>