BACKPORT: coresight: etm4x: Save restore TRFCR_EL1

When the CPU enters a low power mode, the TRFCR_EL1 contents could be
reset. Thus we need to save/restore the TRFCR_EL1 along with the ETM4x
registers to allow the tracing.

The TRFCR related helpers are in a new header file, as we need to use
them for TRBE in the later patches.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20210914102641.1852544-2-suzuki.poulose@arm.com


[Fixed cosmetic details]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
(cherry picked from commit 937d3f58)
[Conflict in in drivers/hwtracing/coresight/coresight-etm4x-core.c,
unnecessary new includes were removed]
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Change-Id: If0d2b8625ffab0bfcd4afbe6fc8c6e7362c01c4a