drm/i915/selftests: Try to recover from a wedged GPU during reset tests

drm/i915/selftests: Try to recover from a wedged GPU during reset tests

If we see the seqno stop progressing, we abandon the test for fear that
the GPU died following the reset. However, during test teardown we still
wait for the GPU to idle before continuing, but we have already
confirmed that the GPU is dead. Furthermore, since we are inside a reset
test, we have disabled the hangchecker, and so there is no safety net and
we wait indefinitely. Detect the stuck GPU and declare it wedged as a
state of emergency so we can escape.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jari Tahvanainen <jari.tahvanainen@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170915130929.18892-1-chris@chris-wilson.co.uk
Tested-by: Jari Tahvanainen <jari.tahvanainen@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>