Revert "i965: Add support for GL_AMD_performance_monitor on Ironlake."

Revert "i965: Add support for GL_AMD_performance_monitor on Ironlake."

This reverts most of commit 0f2da773070c06b6d20ad264d3abb19c4dfd9761.
(I chose to leave the additions to brw_defines.h.)

My previous Ironlake implementation was somewhat broken: counter data
was global, rather than per-context.  This meant that performance
monitors captured data from your compositor, 2D driver, and other 3D
programs.

Originally, I believed that Sandybridge and later had an easy way to
avoid this problem (setting per-context flags in OACONTROL), while
Ironlake did not.  So I'd intended to leave it as a known limitation of
performance monitoring support on Ironlake.  However, this turned out
not to be true.

Unfortunately, our hardware only has one set of aggregating performance
counters shared between all 3D programs, and their values are not saved
or restored by hardware contexts.  Also, at least on Sandybridge and
Ivybridge, the counters lose their values if the GPU goes to sleep.

To work around both of these problems, we have to snapshot the
performance counters at the beginning and end of each batch, similar to
how we handle query objects on platforms that don't support hardware
contexts.

For occlusion queries, this batch bookending approach is fairly simple:
only one occlusion query can be active at a time, and the result is a
single integer.  Performance monitors are more complex: an arbitrary
number of monitors can be active at a time, each monitoring some subset
of our ~30 observability counters.  Individual monitors can be started
and stopped at any point during the batch.  Tracking where each monitor
started/ended relative to batch flushes ends up being a pain.  And you
can run out of space in the buffer.

Properly supporting this required some serious rearchitecting of the
code.  Rather than writing patches to try and morph a broken system into
a working one (which operates quite differently), I decided it would be
simplest to revert the old code and start fresh.  Parts will look
familiar, but other parts are new.

I also decided it would be best to include Sandybridge and Ivybridge
support from the start, since the newer platforms have added complexity
that I wanted to make sure worked.  They're also what most people care
about these days.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>