As noticed by Linus, it is critical that some of the
rwsem constants be signed.  Yet, hex constants are
unsigned unless explicitly casted or negated.

The most critical one is RWSEM_WAITING_BIAS.

This bug was exacerbated by commit
424acaae ("rwsem: wake queued readers
when writer blocks on active read lock")
Signed-off-by: NDavid S. Miller <davem@davemloft.net>