dt-bindings: arm: document the static TPDM compatible

dt-bindings: arm: document the static TPDM compatible

The static TPDM device is intended for sources that do not require MMIO
mapping. Its compatible string should be documented clearly, along with
an example illustrating how to define a static TPDM node in the DT.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20251028-add_static_tpdm_support-v4-1-84e21b98e727@oss.qualcomm.com
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>