update cycle count for imul16

mandel.s

@@ -92,8 +92,8 @@ next:
 positive:
 .endmacro
 
-; min 454 cycles
-; max 756 cycles
+; min 470 cycles
+; max 780 cycles
 .proc imul16
     arg1 = FR0   ; 16-bit arg (clobbered)
     arg2 = FR1   ; 16-bit arg (clobbered)
@@ -112,10 +112,10 @@ positive:
 
     ; unrolled loop for maximum speed, at the cost
     ; of a larger routine
-    ; 424 to 672 cycles
+    ; 440 to 696 cycles
     .repeat 16, bitnum
-        ; first half: 22 to 40 cycles
-        ; second half: 29 to 47 cycles
+        ; bitnum < 8: 25 or 41 cycles
+        ; bitnum >= 8: 30 or 46 cycles
         bitmul16 arg1, arg2, result, bitnum
     .endrepeat