coresight: etm4x: Add sysreg access helpers

mainline inclusion
from mainline-v5.11-rc5
commit 03336d0f
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YCYK
CVE: NA

Reference: https://lore.kernel.org/r/20210110224850.1880240-12-suzuki.poulose@arm.com

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ETM architecture defines the system instructions for accessing
via register accesses. Add basic support for accessing a given
register via system instructions.

We split the list of registers as :
 1) Accessible only from memory mapped interface
 2) Accessible from system register instructions.

All registers are accessible via the memory-mapped interface.
However, some registers are not accessible via the system
instructions. This list is then used to further filter out
the files we expose via sysfs.

Link: https://lore.kernel.org/r/20210110224850.1880240-12-suzuki.poulose@arm.com


Cc: Mike Leach <mike.leach@linaro.org>
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>
Link: https://lore.kernel.org/r/20210201181351.1475223-14-mathieu.poirier@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>