ALSA: hda/hdmi: Limit the maximal count of PCM devices to 8

The current hardware has up to 4 converters. Save little space.
The limit 8 is enough even for a more improved hardware.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220923082236.61024-1-perex@perex.cz


Signed-off-by: Takashi Iwai <tiwai@suse.de>