Current prefetch instruction (dcbt) implementation for IBM POWER8 has wrong
Touch Hint(TH) parameter. The current setting of TH=1 indicates to load data from
current cache line and an unlimited number of sequentially following cache lines.
TTH=0 means to load data from current cache line. rte_prefetch0 function is defined
to load one cache line, which means TH=0 is suited here.