greybus: audio: Avoid using ARA keyword

It is suggested to avoid using ARA keyword externally. So we need to
update GB codec driver. Also, codec name is currently set to 'gb-codec'.
However, it makes more sense to name it as apb-dummy-codec, since it is
used to control various audio modules connected to APB via greybus.

Signed-off-by: Vaibhav Agarwal <vaibhav.agarwal@linaro.org>
Reviewed-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>