ASoC: Intel: Skylake: Merge skl_sst and skl into skl_dev struct

ASoC: Intel: Skylake: Merge skl_sst and skl into skl_dev struct

Skylake driver is divided into two modules:
- snd_soc_skl
- snd_soc_skl_ipc

and nothing would be wrong if not for the fact that both cannot exist
without one another. IPC module is not some kind of extension, as it is
the case for snd_hda_ext_core which is separated from snd_hda_core -
legacy hda interface. It's as much core Skylake module as snd_soc_skl
is.

Statement backed up by existence of circular dependency between this
two. To eliminate said problem, struct skl_sst has been created. From
that very momment, Skylake has been plagued by header errors (incomplete
structs, unknown references etc.) whenever something new is to be added
or code is cleaned up.

As this design is being corrected, struct skl_sst is no longer needed,
so combine it with struct skl. To avoid ambiguity when searching for skl
stuff (struct skl *skl) it has also been renamed to skl_dev.

No functional changes.

Signed-off-by: Piotr Maziarz <piotrx.maziarz@intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lore.kernel.org/r/20190723145854.8527-2-cezary.rojewski@intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>