coresight: etm4x: Add support for sysreg only devices

coresight: etm4x: Add support for sysreg only devices

Add support for devices with system instruction access only.
They don't have a memory mapped interface and thus are not
AMBA devices. System register access is not permitted to
TRCPDCR and thus skip access to them.

Link: https://lore.kernel.org/r/20210110224850.1880240-26-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/20210201181351.1475223-28-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>