fs/ntfs3: Fix error handling in indx_insert_into_root()

There are three bugs in this code:
1) If indx_get_root() fails, then return -EINVAL instead of success.
2) On the "/* make root external */" -EOPNOTSUPP; error path it should
   free "re" but it has a memory leak.
3) If indx_new() fails then it will lead to an error pointer dereference
   when we call put_indx_node().

I've re-written the error handling to be more clear.

Fixes: 82cae269 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>