dmaengine: sun4i: use 'linear_mode' in sun4i_dma_prep_dma_cyclic

dmaengine: sun4i: use 'linear_mode' in sun4i_dma_prep_dma_cyclic

drivers/dma/sun4i-dma.c: In function sun4i_dma_prep_dma_cyclic:
drivers/dma/sun4i-dma.c:672:24: warning:
 variable linear_mode set but not used [-Wunused-but-set-variable]

commit ffc079a4accc ("dmaengine: sun4i: Add support for cyclic requests with dedicated DMA")
involved this, explicitly using the value makes the code more readable.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20200207024445.44600-1-yuehaibing@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>