alsa-mixer: Switch to Headphone when Headphone mic jack is plugged in
When a "Headphone Mic" jack becomes available, we do not know if
a headphone or a mic has been plugged in. Therefore, setting both
paths to "unknown" is, in theory, the correct thing to do.
However, in practice, people are more likely to plug in a headphone
rather than a mic. Therefore, allow autoswitch to the headphone port
when the jack is plugged in.
A more advanced implementation would consider what was plugged in last
time depending on what port was selected on the input side at that
time, and set availability accordingly. However, such an implementation
will have to wait (probably at least until we have our fancy routing
system implementation).
Buglink: https://bugs.launchpad.net/bugs/1169143
Signed-off-by: David Henningsson <david.henningsson@canonical.com>