greybus: audio: Report uevent on GB codec module insertion/removal

GB-Audio-manager module is currently used to report uevent
to above layer in response to any codec module inserted or
removed.

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