alsa: Merge pa_alsa_setting_select with pa_alsa_path_select
As these functions are called together and are related, we might merge
them and call setting_select from pa_alsa_path_select by passing
optional pa_alsa_setting argument.
Make also the setting_select static as it is not called outside of
alsa-mixer.c after this change.
[Additional note from Tanu Kaskinen: this change improves the
mute-during-activation feature, because now the mixer changes related
to selecting the setting happen while the hw is muted.]