ALSA: hda: Avoid WARN_ON() for HDMI chmap slot checks

ALSA: hda: Avoid WARN_ON() for HDMI chmap slot checks

At parsing the channel mapping for HDMI, the current code may spew
WARN_ON() unnecessarily for the case where only invalid (zero) channel
maps are given from the hardware.  Drop WARN_ON() and reorganize the
code a bit for avoiding the hdmi_slot over the array size.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221390
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260428061800.80527-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>