ANDROID: fix kernelci error due to fallthrough

Fix error flagged by kernelci for allmodconfig builds. Need
explicit "fallthrough" statement.

see https://linux.kernelci.org/build/id/62ba68b0fdb9daa19ca39bde/logs/



Fixes: 6bcb2325 ("ANDROID: Add vendor hook to skip usb audio suspend in offload mode")
Signed-off-by: Todd Kjos <tkjos@google.com>
Change-Id: I709ca3ab667cd31f6a9d8c83d48a8223a28dc911