greybus: gb-audio: Clean up codec name generation

Instead of using the fixed suffix, '6-001b', in the
codec name, generate it from the I2S adapter number
and I2C address of the codec.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>