ASoC: SOF: Intel: hdac_ext_stream: consistent prefixes for variables/members

The existing code maximizes confusion by using 'stream' and 'hstream'
variables of different types, e.g:

struct hdac_stream *stream;
struct hdac_ext_stream *stream;
struct hdac_stream *hstream;
struct hdac_ext_stream *hstream;

This confusion is partly inherited from legacy code but SOF
contributors added their own creative spin, e.g.

struct hdac_ext_stream *link_dev;
struct hdac_ext_stream *dsp_stream;
struct hdac_ext_stream hda_stream;

and my personal favorite:

stream = &hda_stream->hda_stream;

This patch suggests a consistent naming across all Intel code related
to HDAudio stream management. The convention is - by hierarchical
order:

struct sof_intel_hda_stream *hda_stream;
struct hdac_ext_stream *hext_stream;
struct hdac_stream *hstream;

No functionality change - just renaming of variables/members.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20220209063104.9971-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>