sha512-s390x.pl: lingering comment update.

crypto/sha/asm/sha512-s390x.pl

@@ -33,7 +33,7 @@
 # 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;