alsa: Move UCM port availability updating to the mixer code

alsa: Move UCM port availability updating to the mixer code

Previously module-alsa-card assigned to pa_alsa_jack.plugged_in
directly, and then did the port availability updating manually. The
idea of pa_alsa_jack_set_plugged_in() is to move the availability
updating to the mixer infrastructure, where it really belongs.

Similarly, pa_alsa_jack.has_control was previously modified directly
from several places. The has_control field affects the port
availability, and pa_alsa_jack_set_has_control() takes care of
updating the availability.

For now, pa_alsa_jack_set_plugged_in() and
pa_alsa_jack_set_has_control() only update the port availability
when using UCM. My plan is to adapt the traditional mixer code later.