ALSA: hda - support writing to the ELD proc file

Allow users to fix quicks of ELD ROMs by writing new values to the ELD proc
interface. The format is one or more lines of "name hex_value".

Users can add/remove/modify up to 32 SAD(Short Audio Descriptor) entries.

Signed-off-by: Wu Fengguang <wfg@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>