It has never been a part of upstream's struct pmu_event. The jevents
utility will not fill this field, so remove it.
They seem to be different. The intent of the alias field was to allow events to have multiple names (I guess). The purpose of the compat field is to allow for mapping events to specific SoCs, rather than CPUs. How this is achieved is not obvious from the commit message, but the compat feature was added much more recently (2020).