maple_tree: move maple_subtree_state from mas_wr_spanning_store to mas_wr_spanning_re...

maple_tree: move maple_subtree_state from mas_wr_spanning_store to mas_wr_spanning_rebalance

Moving the maple_subtree_state is necessary for future cleanups and is
only set up in mas_wr_spanning_rebalance() but never used.

Link: https://lkml.kernel.org/r/20260130205935.2559335-10-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andrew Ballance <andrewjballance@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>