maple_tree: update copyright dates for test code

Add the span to the year of the development.

Link: https://lkml.kernel.org/r/20221025173709.2718725-1-Liam.Howlett@oracle.com


Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>