MLK-20940-3 codecs: cs42xx8: use single read/write to send i2c msg

cs42xx8 will call regcache_sync to refresh its register cache. However,
it will send a long msg which length is greater than the max buffer size
of virtual i2c driver. It will cause the regcache_sync operation failed.
So, use the single read/write to send i2c msg in regcache functions.

Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>