In mipsxx_pmu_map_raw_event(), set event_id to base_id after the cpu
type conditional code to allow that code to override the base_id to use
more bits from the config and a higher bit for parity.
This will allow cores with up to 512 events between all even/odd
counters (an 8-bit event id) such as P5600 to use bit 8 for parity.