sha1-s390x.pl: lingering comment update.

crypto/sha/asm/sha1-s390x.pl

@@ -28,7 +28,8 @@
 # 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.
+# remains z/Architecture specific. On z990 it was measured to peform
+# 23% better than code generated by gcc 4.3.
 
 $kimdfunc=1;	# magic function code for kimd instruction