BACKPORT: staging: goldfish: audio: add devicetree bindings

Introduce devicetree bindings to the Goldfish staging audio driver.

Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Jin Qian <jinqian@android.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 283ded10312a3b75e384313f6f529ec2c636cf2c)

Change-Id: Ib75d3a4cac7353084a8da18a96fb298a759bacc0