sha/asm/sha512p8-ppc.pl: add POWER8 performance data.

# for sha1-ppc.pl - 73%. 100% means that multi-process result equals

# to single-process one, given that all threads end up on the same

# physical core.

#

######################################################################

# Believed-to-be-accurate results in cycles per processed byte [on

# little-endian system]. Numbers in square brackets are for 64-bit

# build of sha512-ppc.pl, presented for reference.

#

#		POWER8

# SHA256	9.9 [15.8]

# SHA512	6.3 [10.3]

$flavour=shift;

$output =shift;