dmaengine: dw: dmamux: Fix device reference leak in rzn1_dmamux_route_allocate

dmaengine: dw: dmamux: Fix device reference leak in rzn1_dmamux_route_allocate

The reference taken by of_find_device_by_node()
must be released when not needed anymore.
Add missing put_device() call to fix device reference leaks.

Fixes: 134d9c52fca2 ("dmaengine: dw: dmamux: Introduce RZN1 DMA router support")
Cc: stable@vger.kernel.org
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20250902090358.2423285-1-linmq006@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>