f2fs: avoid BUG_ON from check_nid_range and update return path in do_read_inode

f2fs: avoid BUG_ON from check_nid_range and update return path in do_read_inode

In function check_nid_range, there is no need to trigger BUG_ON and make kernel stop.
Instead it could just check and indicate the inode number to be EINVAL.
Update the return path in do_read_inode to use the return from check_nid_range.

Signed-off-by: Namjae Jeon <[email protected]>
Signed-off-by: Amit Sahrawat <[email protected]>
[Jaegeuk: replace BUG_ON with WARN_ON]
Signed-off-by: Jaegeuk Kim <[email protected]>