ocfs2: fix error handling in ocfs2_ioctl_move_extents()

ocfs2: fix error handling in ocfs2_ioctl_move_extents()

Smatch complains that if we hit an error (for example if the file is
immutable) then "range" has uninitialized stack data and we copy it to
the user.

I've re-written the error handling to avoid this problem and make it a
little cleaner as well.

Signed-off-by: Dan Carpenter <[email protected]>
Signed-off-by: Jie Liu <[email protected]>
Reviewed-by: Jie Liu <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>