Driver timestamp and sampling period
Improve driver interface by:
Passing sampling period as an argument when enabling performance counters. Even though
PanfrostDriverdoes not use it,
IntelDriverneeds this value for a proper initialization.
Returning a timestamp when dumping performance counters.
PanfrostDriverjust calculates a timestamp and returns it, but
IntelDriverprocess perf records asynchronously, and these records have their own GPU timestamp which should be used instead.