maple_tree: only root node could be deficient

Each level's rightmost node should have (max == ULONG_MAX).  This means
current validation skips the right most node on each level.

Only the root node may be below the minimum data threshold.

Link: https://lkml.kernel.org/r/20241113031616.10530-4-richard.weiyang@gmail.com


Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>