[AMDGPU] Don't rely on !eq comparing int with bits<5>. NFC. (#113279)

Tweak VOP2eInst_Base so that it does not rely on !eq comparing an int
value (-1) with a bits<5> value. This is to avoid a change in behaviour
when #112904 lands, which is a bug fix which has the side effect of
implicitly casting template arguments to the declared template parameter
type.

Author: jayfoad

llvm/lib/Target/AMDGPU/VOP2Instructions.td

@@ -287,7 +287,7 @@ multiclass
 
   let SchedRW = [Write32Bit] in {
     let Uses = !if(useSGPRInput, [VCC, EXEC], [EXEC]) in {
-      if !eq(VOPDOp, -1) then
+      if !empty(VOPDName) then
         def _e32 : VOP2_Pseudo <opName, P>,
                    Commutable_REV<revOp#"_e32", !eq(revOp, opName)>;
       else
@@ -319,7 +319,7 @@ multiclass
 multiclass
     VOP2eInst<string opName, VOPProfile P, SDPatternOperator node = null_frag,
               string revOp = opName, bit useSGPRInput = !eq(P.NumSrcArgs, 3)>
-    : VOP2eInst_Base<opName, P, -1, "", node, revOp, useSGPRInput>;
+    : VOP2eInst_Base<opName, P, 0, "", node, revOp, useSGPRInput>;
 
 multiclass
     VOP2eInst_VOPD<string opName, VOPProfile P, bits<5> VOPDOp, string VOPDName,