Ignore LMP packets without an active link

If we disconnect, we immediately clear the link, but there may still be incoming packets over the PHY. We should just ignore these packets rather than crashing.

Change-Id: I681071476a5b30abbb1c1147d09255d2aae379c4
Merged-In: I681071476a5b30abbb1c1147d09255d2aae379c4
Ignore-AOSP-First: cherry-pick from AOSP
Test: PTS
Bug: 243698555
Bug: 245578454
Tag: #stability