ocfs2: cleanup implemented prototypes

Several prototypes in inode.h are just defined but not actually
implemented and used, so remove them.

Link: http://lkml.kernel.org/r/57763787.4020706@huawei.com
Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>