[LangRef] Update saturating examples for llvm.smul.fix.sat. NFC

Some saturation examples for llvm.smul.fix.sat were not showing
the correct result. I've adjusted the operands to make sure that
we actually trigger overflow in those examples.

llvm-svn: 370566

llvm/docs/LangRef.rst

@@ -13754,9 +13754,9 @@ Examples
 
       ; Saturation
       %res = call i4 @llvm.smul.fix.sat.i4(i4 7, i4 2, i32 0)  ; %res = 7
-      %res = call i4 @llvm.smul.fix.sat.i4(i4 7, i4 2, i32 2)  ; %res = 7
-      %res = call i4 @llvm.smul.fix.sat.i4(i4 -8, i4 2, i32 2)  ; %res = -8
-      %res = call i4 @llvm.smul.fix.sat.i4(i4 -8, i4 -2, i32 2)  ; %res = 7
+      %res = call i4 @llvm.smul.fix.sat.i4(i4 7, i4 4, i32 2)  ; %res = 7
+      %res = call i4 @llvm.smul.fix.sat.i4(i4 -8, i4 5, i32 2)  ; %res = -8
+      %res = call i4 @llvm.smul.fix.sat.i4(i4 -8, i4 -2, i32 1)  ; %res = 7
 
       ; Scale can affect the saturation result
       %res = call i4 @llvm.smul.fix.sat.i4(i4 2, i4 4, i32 0)  ; %res = 7 (2 x 4 -> clamped to 7)