UPSTREAM: coresight: etm-perf: Add support for ETR backend

Add support for using TMC-ETR as backend for ETM perf tracing.
We use software double buffering at the moment. i.e, the TMC-ETR
uses a separate buffer than the perf ring buffer. The data is
copied to the perf ring buffer once a session completes.

The TMC-ETR would try to match the larger of perf ring buffer
or the ETR buffer size configured via sysfs, scaling down to
a minimum limit of 1MB.

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 22f429f19c4135d51e9dcaf360c0920e32aac7f9).

Bug: 140266694
Change-Id: I41669d685143bbc9bdd6e18fe02274fcb4445f6c
Signed-off-by: Yabin Cui <yabinc@google.com>