drm/i915: Do not allow unwedging following a failed driver initialisation

If we declare the driver wedged during early initialisation, we leave
the driver in an undefined state (with respect to GEM execution). As
this leads to unexpected behaviour if we allow the user to unwedge the
device (through debugfs, and performed by igt at test start), do not.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190103213340.1669-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3380,6 +3380,9 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 	if (!test_bit(I915_WEDGED, &i915->gpu_error.flags))
 		return true;
 
+	if (!i915->gt.scratch) /* Never full initialised, recovery impossible */
+		return false;
+
 	GEM_TRACE("start\n");
 
 	/*