maple_tree: fix typos/spellos etc

Fix typos/grammar and spellos in documentation.

Link: https://lkml.kernel.org/r/20231210063839.29967-1-rdunlap@infradead.org


Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>