drm/i915: Show IPEIR and IPEHR in the engine dump

drm/i915: Show IPEIR and IPEHR in the engine dump

A useful bit of information for inspecting GPU stalls from
intel_engine_dump() are the error registers, IPEIR and IPEHR.

v2: Fixup gen changes in register offsets (Tvrtko)
v3: Old FADDR location as well
v4: Use I915_READ64_2x32

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171218123914.19027-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>