Since with multiple devices, we may have multiple different perf_pmu
each with their own type, we want to find the right one for the job.

The tests are run with a specific fd, from which we can extract the
appropriate bus-id and find the associated perf-type. The performance
monitoring tools are a little more general and not yet ready to probe
all device or bind to one in particular, so we just assume the default
igfx for the time being.

v2: Extract the bus address from out of sysfs
v3: A new name for a new decade!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Robert M. Fosha" <robert.m.fosha@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: "Robert M. Fosha" <robert.m.fosha@intel.com> #v2
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>