ASoC: mchp-spdiftx: Do not set Validity bit(s)

The Validity bits (bit 28) must not be set in order to have the samples
valid. Some controllers look for this bit and ignore the samples if it
is set.

Fixes: 06ca24e9

 ("ASoC: mchp-spdiftx: add driver for S/PDIF TX Controller")
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Link: https://lore.kernel.org/r/20201104155738.68403-1-codrin.ciubotariu@microchip.com


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