ocfs2: do not fallback to buffer I/O write if appending

ocfs2: do not fallback to buffer I/O write if appending

Now we can do direct io and do not fallback to buffered IO any more in
case of append O_DIRECT write.

Signed-off-by: Joseph Qi <[email protected]>
Cc: Weiwei Wang <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Xuejiufei <[email protected]>
Cc: alex chen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>