mas_erase() may not deal correctly with all maple states.  Make the
function more robust by ensuring the state is in one of the two acceptable
states.

Link: https://lkml.kernel.org/r/20231101171629.3612299-3-Liam.Howlett@oracle.comSigned-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>