ALSA: hda - Fix missing CA initialization for HDMI/DP

The commit 53d7d69d
    ALSA: hdmi - support infoframe for DisplayPort
dropped the initialization of CA field accidentally.
This resulted in only two-channel LPCM mode on Nvidia machines.

Reference: kernel bug 28592
	https://bugzilla.kernel.org/show_bug.cgi?id=28592



Signed-off-by: Takashi Iwai <tiwai@suse.de>
Cc: <stable@kernel.org>