firmware: cs_dsp: Add memory chunk helpers

firmware: cs_dsp: Add memory chunk helpers

Add helpers that can be layered on top of a buffer read from or to be
written to the DSP to faciliate accessing datastructures within the DSP
memory. These functions handle adding the padding bytes for the DSP,
converting to big endian, and packing arbitrary length data.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220722094851.92521-2-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>