i965: Remove perf monitor/query backend

i965: Remove perf monitor/query backend

In its current state the unified i965 backend for
AMD_performance_monitor and INTEL_performance_query isn't able to report
meaningful Observation Architecture metrics since we haven't so far had
the necessary kernel support to fully configure the OA unit, nor the
corresponding support for normalizing the counters into a form that can
be usefully interpreted by application developers (as opposed to raw
values that may, for example, scale by the number of EUs there are).

So that we can focus on implementing just one of these extensions fully
and since we anticipate some significant backend changes as we look to
use a new kernel interface to configure the OA unit, this patch removes
the current backend. This will simplify our ability to update the
frontend infrastructure and backend interface before updating our
support for performance counters.

Signed-off-by: Robert Bragg <robert@sixbynine.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>