ALSA: hda - Proper power-map toggling for input pins

The current code overrides the event type on input pins always to
PWR_EVENT.  Although this still works (PWR_EVENT and INSERT_EVENT
are handled samely), it'd be better to avoid such overrides.

Also, currently the unsol events are registered even for fixed pins
which will never raise the pin-detection event.

This patch fixes both issues.

Signed-off-by: Takashi Iwai <tiwai@suse.de>