msm: rtb: record counter timestamp for every log record

Record counter timestamp in every RTB log record to help
correlate these events with other subsystem events which
occur outside of cpu subsystem.

Change-Id: Ib1291524c53c4ec757a494a1e08cb0925720e1a6
Signed-off-by: Srinivas Ramana <sramana@codeaurora.org>