ASoC: mmp-sspa: Drop S20_3LE case

It does nothing, because the corresponding bit s not flipped on in .formats
and the audio SRAM DMA engine is not able to handle 20-bit transfers
anyway.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Link: https://lore.kernel.org/r/20200511210134.1224532-3-lkundrak@v3.sk


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