ALSA: hda - Fix missing ADC list in ALC260 auto-probe mode

The commit f9e336f6
    ALSA: hda - Unify capture mixer creation in realtek codes
removed the ADC check for ALC260 auto-probe mode accidentally.
Re-added to patch_alc260() again.

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