ASoC: gtm601: Document GTM601 bindings
ASoC: gtm601: Document GTM601 bindings

Add small documentation for GTM601 UMTS modem audio interface.

Signed-off-by: Marek Belisko <e54ec4e8b56ff7382fb135e028860ad99be4caf9@goldelico.com>
Signed-off-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs