ASoC: mchp-spdiftx: use FIELD_PREP() where possible

Use directly FIELD_PREP() marco where possible. There is no need for
the extra wrappers.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230301113807.24036-2-claudiu.beznea@microchip.com


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