drm/i915: Fix uninitialised variable in intel_context_create_request.

In case backoff fails with an error, we return an undefined rq,
assign err to rq correctly.

Fixes: 8a929c9e ("drm/i915: Use ww pinning for intel_context_create_request()")
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200918111208.1392128-1-maarten.lankhorst@linux.intel.comReviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/gt/intel_context.c

@@ -472,6 +472,7 @@ struct i915_request *intel_context_create_request(struct intel_context *ce)
 		err = i915_gem_ww_ctx_backoff(&ww);
 		if (!err)
 			goto retry;
+		rq = ERR_PTR(err);
 	} else {
 		rq = ERR_PTR(err);
 	}