greybus: audio: Remove the MODULE_LICENSE()

This is not a kernel module. It should not use
the module license macro.
Signed-off-by: Phong Tran <tranmanphong@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/audio.c

@@ -470,6 +470,3 @@ void gb_audio_protocol_exit(void)
 	gb_protocol_deregister(&gb_i2s_receiver_protocol);
 	gb_protocol_deregister(&gb_i2s_mgmt_protocol);
 }
-
-
-MODULE_LICENSE("GPL");