dmaengine: stm32: dmamux: fix OF node leak on route allocation failure

Make sure to drop the reference taken to the DMA master OF node also on
late route allocation failures.

Fixes: df7e762 ("dmaengine: Add STM32 DMAMUX driver")
Cc: stable@vger.kernel.org      # 4.15
Cc: Pierre-Yves MORDRET <pierre-yves.mordret@foss.st.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://patch.msgid.link/20251117161258.10679-12-johan@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: jhovold

drivers/dma/stm32/stm32-dmamux.c

@@ -143,7 +143,7 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
 	ret = pm_runtime_resume_and_get(&pdev->dev);
 	if (ret < 0) {
 		spin_unlock_irqrestore(&dmamux->lock, flags);
-		goto error;
+		goto err_put_dma_spec_np;
 	}
 	spin_unlock_irqrestore(&dmamux->lock, flags);
 
@@ -165,6 +165,8 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
 
 	return mux;
 
+err_put_dma_spec_np:
+	of_node_put(dma_spec->np);
 error:
 	clear_bit(mux->chan_id, dmamux->dma_inuse);