Update pre8

crypto/modes/asm/ghashp8-ppc.pl

@@ -30,7 +30,7 @@
 # 2x aggregated reduction improves performance by 50% (resulting
 # performance on POWER8 is 1 cycle per processed byte), and 4x
 # aggregated reduction - by 170% or 2.7x (resulting in 0.55 cpb).
-# POWER9 delivers 0.40 cpb.
+# POWER9 delivers 0.51 cpb.
 
 $flavour=shift;
 $output =shift;