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

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

commit b1b590a590af13ded598e70f0b72bc1e515787a1 upstream.

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

Fixes: df7e762db5f6 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>