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

dmaengine: dw: 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: 134d9c52fca2 ("dmaengine: dw: dmamux: Introduce RZN1 DMA router support")
Cc: stable@vger.kernel.org	# 5.19
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://patch.msgid.link/20251117161258.10679-6-johan@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>