UPSTREAM: coresight: tmc-etr: Relax collection of trace from sysfs mode

Since the ETR now uses mode specific buffers, we can reliably
provide the trace data captured in sysfs mode, even when the ETR
is operating in PERF mode.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(Upstream commit cad5f8d399bbe3c4ed61a21f649d61b09f6efb7b).

Bug: 140266694
Change-Id: Ic7ac02c4d80fe00b469d05b1abe779f9f177362b
Signed-off-by: Yabin Cui <yabinc@google.com>