r252680:
Fix SIM lock not owned panic
The CAM locking requirements of registering an async
callback has changed so the SIM lock must be held. Remove
code that explicitly dropped the lock around the register.
Also return CAM_SEL_TIMEOUT instead of CAM_TID_INVALID
for bad targets to avoid a lot console spam during bus
scans.
MFC after: 1 month
4d5919ec0b