Right now the direction of a DAI has to be specified as a literal
number in the device tree, e.g.:

	dai@0 {
		reg = <0>;
		direction = <2>;
	};

but this does not make it immediately clear that this is a
playback/RX-only DAI.

Actually, q6asm-dai.c has useful defines for this. Move them to the
dt-bindings header to allow using them in the dts(i) files.
The example above then becomes:

	dai@0 {
		reg = <0>;
		direction = <Q6ASM_DAI_RX>;
	};

which is immediately recognizable as playback/RX-only DAI.
Signed-off-by: NStephan Gerhold <stephan@gerhold.net>
Reviewed-by: NSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200727082502.2341-1-stephan@gerhold.netSigned-off-by: NMark Brown <broonie@kernel.org>