firmware: cs_dsp: Rename KConfig symbol CS_DSP -> FW_CS_DSP

Qualify the KConfig symbol for cs_dsp by adding a FW_ prefix so that
it is more explicit what is being referred to. This is preparation for
using the symbol to namespace the exports.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20221124134556.3343784-2-rf@opensource.cirrus.com


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