f2fs: add a function to move nid

This patch add a new function to move nid from one state to another.
Move operation is heavily used, by adding a new function for it
we can cut down some branches from several flow.

Signed-off-by: Fan li <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>
1 file changed