coresight: etm4x: Add necessary synchronization for sysreg access

mainline inclusion
from mainline-v5.11-rc5
commit 1ab3bb9d
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YCYK
CVE: NA

Reference: https://lore.kernel.org/r/20210110224850.1880240-22-suzuki.poulose@arm.com

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As per the specification any update to the TRCPRGCTLR must be synchronized
by a context synchronization event (in our case an explicist ISB) before
the TRCSTATR is checked.

Link: https://lore.kernel.org/r/20210110224850.1880240-22-suzuki.poulose@arm.com


Cc: Mike Leach <mike.leach@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/20210201181351.1475223-24-mathieu.poirier@linaro.org


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