ASoC: dt-bindings: Introduce compatible string for imx8qm

Register map for i.MX8QM is similar with i.MX6 series. Integration
of SAI IP into i.MX8QM SOC features a FIFO size of 64 X 32 bits samples.

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://lore.kernel.org/r/20190814082911.665-3-daniel.baluta@nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>