dmaengine: imx-dma: Remove unused .id_table

Since 5.10-rc1 i.MX is a devicetree-only platform, so simplify the code
by removing the unused non-DT support.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20201124143405.2764-1-festevam@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>