Don't enumerate via_hp_mixer while hp_mux is null (headphone does not exist),
to fix the crash of via_independent_hp_info (via_hp_mixer's .info), which will
reference hp_mux.
Signed-off-by: NLogan Li <LoganLi@viatech.com.cn>
Signed-off-by: NHarald Welte <HaraldWelte@viatech.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@perex.cz>