Alan Cox reported that lockdep runs out of its stack-trace entries
with certain configs:

 BUG: MAX_STACK_TRACE_ENTRIES too low

This happens because there are 1024 hash buckets, each with a
separate lock. Lockdep puts each lock into a separate lock class and
tracks them independently.

But in reality we never take more than one of the buckets, so they
really belong into a single lock-class. Annotate the has bucket lock
init accordingly.

[ Impact: reduce the lockdep footprint of dma-debug ]
Reported-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>