ASoC: dt-bindings: add TDM slot idle mode properties

ASoC: dt-bindings: add TDM slot idle mode properties

Add properties to describe TDM slot idle behaviour. These properties can
be used to describe how a DAI is supposed to behave when not active.

For example, Apple Silicon laptops split a single I2S bus between two
physical lines which are combined at an OR gate in front of the
receiving port. One codec on each line is expected to transmit zeroes
during the active TDM slots of the opposite line, or we will have corrupted
data at the receiver.

Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260301-tdm-idle-slots-v3-3-c6ac5351489a@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>