In the end we already enabled the sync-write mode for most of HD-audio
controllers including Intel, and it's no big merit to keep the async
write mode for the rest.  Let's make it as default and drop the
superfluous AZX_DCAPS_SYNC_WRITE bit flag.

Also, avoid to set the allow_bus_reset flag, which is a quite unstable
and hackish behavior that was needed only for some early platforms
(decades ago).  The straight fallback to the single cmd mode is more
robust.

Link: https://lore.kernel.org/r/20200618144051.7415-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>