Added file with common properties for cortex-m cores.
Added optional swo-ref-frequency property.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
compatible = "arm,cortex-m33f" was already used for some time
(lpc55S6x, nrf9160...) without any related bindings.
Every works fine until you need to access one CPU node property
(eg. clock-frequency)...
Signed-off-by: Arnaud Mouiche <arnaud.mouiche@invoxia.com>