ALSA: hda: cs35l41: change cs35l41_prop_model to static

cs35l41_prop_model is only used in cs35l41_hda_property.c now,
change it to static.

Fixes: ef4ba63f

 ("ALSA: hda: cs35l41: Support systems with missing _DSD properties")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20230817014252.1511232-1-yangyingliang@huawei.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>