maple_tree: use maple state end for write operations

ma_wr_state was previously tracking the end of the node for writing. 
Since the implementation of the ma_state end tracking, this is duplicated
work.  This patch removes the maple write state tracking of the end of the
node and uses the maple state end instead.

Link: https://lkml.kernel.org/r/20231101171629.3612299-11-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>