Do not fallback HFP active device to watches

Usually users do not expect a call gets routed to the watch
automatically. Watches usually have speaker instead of earpiece,
fallbacking the audio to a watch could lead to privacy issues.

Tag: #compatibility
Bug: 256657323
Test: atest HeadsetServiceTest
Change-Id: I3fa1364c09674c1b6b817c783d4d1e2ecbca901a