Some minor SDCA preparation

Some minor SDCA preparation

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

Make some small fixups and add some minor missing features that will be
needed for the next major part of the SDCA work. This series doesn't do
a lot on its own, but as the next series will add all the ALSA control
and DAPM graph creation it's probably best to get these minor things out
of the way to simplify review on the bigger stuff.