ALSA: hda - Clean up Realtek auto-mute unsol routines

Most of unsol handlers defined in patch_realtek.c can be classified to
two types, mute via amp of pins and mute via ctl bits of pins.
Thus there are a big room to generalize each implementation.

This patch creates two generic functions, alc_automute_amp() and
alc_automute_pin().  The latter is actually changed from the previous
alc_sku_automute().  Each caller needs to initialize hp_pins and
speaker_pins properly at own init_hook.

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