ocfs2/dlm: fix a typo in dlmcommon.h

Refer to cluster/tcp.h, NET_MAX_PAYLOAD_BYTES is a typo for
O2NET_MAX_PAYLOAD_BYTES.

Since currently DLM_MIG_LOCKRES_RESERVED is not actually used, it won't
cause any problem.  But we'd better correct it for further use.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>