Re-route lock moved outside ma_device_reinit__aaudio call to avoid potential race condition. Also cleaned up the reroute code a bit.

AAudio: Prevent re-routing while tearing down device. Fixes a crash where re-route thread would read ma_device while being destroyed from main thread.

This checks the result of reading from the decoder when asynchronously
loading a file. In practice the existing check already covers this, but
it's technically possible for an error result the be skipped over.

This will abort reading early if the underlying data source returns an
error.

Thanks to the Clang static analyzer for this one!

This did not affect functionality at all because the implementation of
the relevant function is just a simple bitwise OR.

Improved synchronization for AAudio rerouting. This should fix the crash observed in ma_device_init__aaudio (when re-routing).

This is only very basic right now. Will be expanded on later.