maple_tree: Rewrite mas_data_end to return slot not occupied count.

maple_tree: Rewrite mas_data_end to return slot not occupied count.

Rewrite mas_data_end to return slot, not occupied count and fix coalesce
calculation for a run of NULLs, etc

Move MT_BUG_ON for use in verification functions.

Add mas_mn for easier mas->node enode to node conversion.

Drop __mte_get_rcu_slot as the dead_node detect doesn't work right.

Make sure hard_data doesn't return a negative.

Fix ma_state on calls to mas_update_gaps

Fix end pivots on the right side of a split.

Fix number of slots being occupied calculation when _mas_add is using
the last slot and the new range doesn't run to mas->max.

Fix mas_rebalance when right node is empty and fix mas_data_end uses.

Rewrite mas_coalesce for new mas_data_end uses.

Fix mt_find overflow of index when there is a valuse at ULONG_MAX.

Add a testcase for mt_find overflow.

Fix mas_rev_awalk to check for errors prior to trying to walk.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>