dmaengine: imx-sdma: Only check ratio on parts that support 1:1

On imx8mq B0 chip, AHB/SDMA clock ratio 2:1 can't be supported,
since SDMA clock ratio has to be increased to 250Mhz, AHB can't reach
to 500Mhz, so use 1:1 instead.

To limit this change to the imx8mq for now this patch also adds an
im8mq-sdma compatible string.

Signed-off-by: Angus Ainslie (Purism) <angus@akkea.ca>
Acked-by: Robin Gong <yibin.gong@nxp.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>