maple_tree: testing fix for spanning store on 32b

maple_tree: testing fix for spanning store on 32b

32 bit nodes have a larger branching factor.  This affects the required
value to cause a height change.  Update the spanning store height test to
work for both 64 and 32 bit nodes.

Link: https://lkml.kernel.org/r/20250828003023.418966-3-Liam.Howlett@oracle.com
Fixes: f9d3a963fef4 ("maple_tree: use height and depth consistently")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>