firmware: cs_dsp: tidy includes in cs_dsp.c and cs_dsp.h

This patch removes unused included header files and moves others into
cs_dsp.h to ensure that types referenced in the header file are properly
described to prevent compiler warnings.

Signed-off-by: Simon Trimmer <simont@opensource.cirrus.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20211115120215.56824-1-simont@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>