soundtrigger: Fall back to V2.0 if V2.1 is not present

A device may not be configured to ship with ST V2.1 impl,
in this case the device will stuck in a boot loop because the
framework will be attempting to instantiate ST, but the
service will not have ST server side registered.

Since the service code is the same for all devices,
allow a fallback to ST V2.0. This way, if only V2.0 is present
on the device, it will be registered, and the framework
will find it. The actual version used can be determined by
examining output of 'lshal' command.

Also remove obsolete dependency on broadcast radio.

Bug: 63600413
Bug: 68823037
Test: Try taimen both with ST V2.0 and V2.1 impls
Change-Id: I484659b1df5a7e4b11db91d0cf75a7079786c766