i965: Use updated kernel interface for accurate TIMESTAMP reads

i965: Use updated kernel interface for accurate TIMESTAMP reads

I was mistaken, I thought we already had fixed this in the kernel a
couple of years ago. We had not, and the broken read (the hardware
shifts the register output on 64bit kernels, but not on 32bit kernels) is
now enshrined into the ABI. I also had the buggy architecture reversed,
believing it to be 32bit that had the shifted results. On the basis of
those mistakes, I wrote

commit c8d3ebaffc0d7d915c1c19d54dba61fd1e57b338
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Wed Apr 29 13:32:38 2015 +0100

    i965: Query whether we have kernel support for the TIMESTAMP register once

Now that we do have an extended register read interface for always
reporting the full 36bit TIMESTAMP (irrespective of whether the hardware
is buggy or not), make use of it and in the process fix my reversed
detection of the buggy reads for unpatched kernels.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Martin Peres <martin.peres@linux.intel.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Tested-and-acked-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>