cmd/compile: remove reduntant Zero rule

These two rules produce the same output but have opposite
s%16 conditions. Consolidate them into a single rule.

Change-Id: I6daa0e7f7af4a4e59a3125b66b85f59e888586c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/640475
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: jake-ciolek

src/cmd/compile/internal/ssa/_gen/AMD64.rules

@@ -404,11 +404,7 @@
 		(MOVQstoreconst [makeValAndOff(0,0)] destptr mem))
 
 // Adjust zeros to be a multiple of 16 bytes.
-(Zero [s] destptr mem) && s%16 != 0 && s > 16 && s%16 > 8 && config.useSSE =>
-	(Zero [s-s%16] (OffPtr <destptr.Type> destptr [s%16])
-		(MOVOstoreconst [makeValAndOff(0,0)] destptr mem))
-
-(Zero [s] destptr mem) && s%16 != 0 && s > 16 && s%16 <= 8 && config.useSSE =>
+(Zero [s] destptr mem) && s%16 != 0 && s > 16 && config.useSSE =>
 	(Zero [s-s%16] (OffPtr <destptr.Type> destptr [s%16])
 		(MOVOstoreconst [makeValAndOff(0,0)] destptr mem))