tsx, locking: Handle lockref locks

The lockref cmpxchg fast path got disabled for spinlocks >= 4 bytes.
The elided spinlock is 8 bytes, so it suffered from this fate. However
the new fields beyond 4 bytes are merely book keeping for adaptation,
which does not directly contribute to the atomic state of the lock.

So the original lockref code still works, even though it only
covers the first 4 bytes of the lock.

Adjust the lockref enabling to special case RTM_LOCKS.

Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>