maple_tree: don't set a new maximum on the node when not reusing nodes

In RCU mode, the node limits were being updated to the last pivot which
may not be correct and would cause the metadata to be set when it
shouldn't.  Fix this by not setting a new limit in this case.

Link: https://lkml.kernel.org/r/20221107163857.867377-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>