ALSA: hda - Set single_adc_amp flag for CS420x codecs

commit bad994f5b4ab57eec8d56c180edca00505c3eeb2 upstream.

CS420x codecs seem to deal only the single amps of ADC nodes even
though the nodes receive multiple inputs.  This leads to the
inconsistent amp value after S3/S4 resume, for example.

The fix is just to set codec->single_adc_amp flag.  Then the driver
handles these ADC amps as if single connections.

Reported-and-tested-by: Vasil Zlatanov <vasil.zlatanov@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>