intel: Add .aub file output support.

This will allow the driver to capture all of its execution state to a
file for later debugging.  intel_gpu_dump is limited in that it only
captures batchbuffers, and Mesa's captures, while more complete, still
capture only a portion of the state involved in execution.

This is a squash commit of a long series of hacking as we tried to get
the resulting traces to work in the internal simulator.  It contains
contributions by Yuanhan Liu and Kenneth Graunke.

v2: Drop the MI_FLUSH_ENABLE setup.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>