sha512-s390x.pl: lingering comment update.

# instructions and achieve "64-bit" performance even in 31-bit legacy

# application context. The feature is not specific to any particular

# processor, as long as it's "z-CPU". Latter implies that the code

# remains z/Architecture specific. On z900 SHA256 was measured to

# remains z/Architecture specific. On z990 SHA256 was measured to

# perform 2.4x and SHA512 - 13x better than code generated by gcc 4.3.

$flavour = shift;