We tracked down the first-0.5s-hdmi-audio-samples-lost problem to the
AC_VERB_SET_CHANNEL_STREAMID command. It is suspected that many HDMI
sinks need some time to adapt to the new state.

The workaround is to avoid changing stream id/format whenever possible.
Proposed by David.
Signed-off-by: NDavid Härdeman <david@hardeman.nu>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>