dmaengine: Remove unused declaration dma_chan_cleanup()

Commit f27c580c

 ("dmaengine: remove 'bigref' infrastructure")
removed the implementation but left declaration in place. Remove it.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230809080012.22000-1-yuehaibing@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>