coresight: etm4x: Fix number of resources check for ETM 4.3 and above

The initialisation code checks TRCIDR4 to determine the number of resource
selectors available on the system. Since ETM v 4.3, the value 0 has a
different meaning. This patch takes into account this change.

Signed-off-by: Mike Leach <mike.leach@linaro.org>
[Removed '.' in patch title, added stable]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200916191737.4001561-17-mathieu.poirier@linaro.org


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