When the TRBE is stopped on truncating an event, we may not
set the FORMAT flag, even though the size of the record is 0.
Let us be consistent and not confuse the user.

To ensure that the format flag is always set on all the
records generated by TRBE, set the flag when we have a
new handle. Rather than deferring to the "end" operation,
which makes it clear. So, we can do this from

 -  arm_trbe_enable() -> When a new handle is provided by the
    CoreSight PMU, triggered via etm_event_start()
 -  trbe_handle_overflow() -> When we begin a new handle after
    closing the previous on overflow.

Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20210914102641.1852544-5-suzuki.poulose@arm.com
[Fixed inverted words in title]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>