ALSA: hda - make HDMI messages more user friendly

- make some messages more user friendly
- add message prefix "HDMI:" to indicate the problem's domain
  (also easier to do `dmesg | grep HDMI` ;-)

Signed-off-by: Wu Fengguang <wfg@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>