lglock: remove unused DEFINE_LGLOCK_LOCKDEP()

struct lglocks use their own lock_key/lock_dep_map which are defined in
struct lglock.  DEFINE_LGLOCK_LOCKDEP() is unused, so remove it and save a
small piece of memory.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>