IB/uverbs: Make lockdep output more readable

Add names for our lockdep classes, so instead of having to decipher
lockdep output with mysterious names:

    Chain exists of:
      key#14 --> key#11 --> key#13

lockdep will give us something nicer:

    Chain exists of:
      SRQ-uobj --> PD-uobj --> CQ-uobj

Signed-off-by: Roland Dreier <roland@purestorage.com>