ALSA: ice1712: Add support for Edirol DA-2496

This device is similar to the M-Audio Delta 1010LT in that it uses the
AK4524VF ADC/DAC, but it does not use the CS8427 for SPDIF.

The SPDIF appears to be set up correctly, but I am not able to test it
as I do not have any devices that use it.

This patch makes the ADC/DAC's and the hardware mixer visible to apps
such as alsamixer and envy24control.

Signed-off-by: Garnet MacPhee <dhubsith@comcast.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>