gve: unlink old napi only if page pool exists

Commit de70981 ("gve: unlink old napi when stopping a queue using
queue API") unlinks the old napi when stopping a queue. But this breaks
QPL mode of the driver which does not use page pool. Fix this by checking
that there's a page pool associated with the ring.

Cc: stable@vger.kernel.org
Fixes: de70981 ("gve: unlink old napi when stopping a queue using queue API")
Reviewed-by: Joshua Washington <joshwash@google.com>
Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250317214141.286854-1-hramamurthy@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: hramamurthy12

drivers/net/ethernet/google/gve/gve_rx_dqo.c

@@ -114,7 +114,8 @@ void gve_rx_stop_ring_dqo(struct gve_priv *priv, int idx)
 	if (!gve_rx_was_added_to_block(priv, idx))
 		return;
 
-	page_pool_disable_direct_recycling(rx->dqo.page_pool);
+	if (rx->dqo.page_pool)
+		page_pool_disable_direct_recycling(rx->dqo.page_pool);
 	gve_remove_napi(priv, ntfy_idx);
 	gve_rx_remove_from_block(priv, idx);
 	gve_rx_reset_ring_dqo(priv, idx);