perf cs-etm: Pass unformatted flag to decoder

The TRBE (Trace Buffer Extension) feature allows a separate trace buffer
for each trace source, therefore the trace wouldn't need to be
formatted. The driver was introduced in commit 3fbf7f01
("coresight: sink: Add TRBE driver").

The formatted/unformatted mode is encoded in one of the flags of the
AUX record. The first AUX record encountered for each event is used to
determine the mode, and this will persist for the remaining trace that
is either decoded or dumped.

Signed-off-by: James Clark <james.clark@arm.com>