[ALSA] emu10k1: Rename the digital optical capture control for the Audigy 2 ZS

Notebook.
Digital playback and capture now works, but it is not bit accurate because it
passes through a resampler.
Bit accurate playback and capture will be implemented later via the p17v.

Signed-off-by: James Courtier-Dutton <James@superbug.co.uk>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>