#270 operf cannot profile in timer mode

[Maynard Johnson]

In some situations, operf may not be able to recognize a processor type so it just prints the message
Unable to ascertain cpu type. Exiting
and gives up. This is because the only profiling mode operf has is hardware event-based profiling (e.g., cycles, cache misses, instructions completed, etc.). Each of these hardware events have a particular code, based on the processor type, which can be used by operf to "program" the performance monitor unit to collect profile information for that event. If the processor type cannot be determined, we have no way of knowing what events are available or what event codes are valid. In such a case, it would be preferable if operf could fall back to a timer-based profiling mode.