lockd: move struct nlm_wait to lockd.h

The next patch needs struct nlm_wait in fs/lockd/clntproc.c, so move
the definition to a shared header file. As an added clean-up, drop
the unused b_reclaim field.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>