staging: greybus: audio: Enable GB codec, audio module compilation.

Currently you can't enable the Gey Bus Audio Codec because there is no
entry for it in the Kconfig file. Originally the config name was going
to be AUDIO_MSM8994 but that's not correct because other types of
hardware are supported now. I have chosen the name AUDIO_APB_CODEC
instead.  Also I had to update the dependencies for GREYBUS_AUDIO to
make the compile work.

Signed-off-by: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/2b50959ccffe5a4372880d27e79ef3be1873372c.1594290158.git.vaibhav.sr@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>