ASoC: fix typo and removed unneeded switch case for cs4270

This removes a misspelled comment and got rid of superfluous switch
case.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Acked-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>