drm/msm/gem: Fix error return on fence id alloc fail

This was a typo, we didn't actually want to return zero.

Fixes: a61acbbe ("drm/msm: Track "seqno" fences by idr")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/491145/
Link: https://lore.kernel.org/r/20220624184528.4036837-1-robdclark@gmail.com

drivers/gpu/drm/msm/msm_gem_submit.c

@@ -928,7 +928,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
 						    INT_MAX, GFP_KERNEL);
 	}
 	if (submit->fence_id < 0) {
-		ret = submit->fence_id = 0;
+		ret = submit->fence_id;
 		submit->fence_id = 0;
 	}