ocfs2: change incorrect 'extern' keyword to 'static' in dlmfs

Change function param_set_dlmfs_capabilities from 'extern' to 'static' since
function param_get_dlmfs_capabilities is also 'static'.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>