maple_tree: we don't set offset to MAPLE_NODE_SLOTS on error

maple_tree: we don't set offset to MAPLE_NODE_SLOTS on error

When mas_anode_descend() not find gap, it sets -EBUSY instead of setting
offset to MAPLE_NODE_SLOTS.

Link: https://lkml.kernel.org/r/20241116014805.11547-4-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>