The call to mte_set_dead_node() before the smp_wmb() already calls
smp_wmb() so this is not needed. This is an optimization for the RCU
mode of the maple tree.
Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam Howlett <Liam.Howlett@oracle.com>