Add SDCA UMP/FDL support

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

Next installment of the SDCA changes, hopefully the next series after
this should be the full class driver. It is worth noting this series has
a build dependency on a patch working its way through the PM/ACPI tree:

commit ac46f5b6c661 ("ACPICA: Add SoundWire File Table (SWFT) signature")
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git

But we can probably worry about that later, as normally there is a
reasonable amount of review on these SDCA series'.

This series broadly breaks down into 3 chunks, first there are several
changes to remove the assumption that the struct device used for SDCA
purposes represents the SoundWire slave. This is because the SDCA class
driver will be made of an auxiliary driver for each SDCA Function, thus
the SoundWire slave will be on the parent device for each individual
driver. Then there are patches to add support for UMP/FDL. And then
finally since the rest of the HID support is there and UMP was the last
missing part required a small patch to add a function to allow reporting
of HID events from SDCA devices.