AMDGPU: Use defvar instead of defaulted multiclass argument

Author: arsenm

llvm/lib/Target/AMDGPU/VOP3PInstructions.td

@@ -681,8 +681,9 @@ class MAIInst<string OpName, VOPProfile P, SDPatternOperator node>
   bit is_gfx940_xdl = 0;
 }
 
-multiclass MAIInst<string OpName, string P, SDPatternOperator node,
-                   bit NoDstOverlap = !cast<VOPProfileMAI>("VOPProfileMAI_" # P).NoDstOverlap> {
+multiclass MAIInst<string OpName, string P, SDPatternOperator node> {
+  defvar NoDstOverlap = !cast<VOPProfileMAI>("VOPProfileMAI_" # P).NoDstOverlap;
+
   let isConvergent = 1, mayRaiseFPException = 0, ReadsModeReg = 1 in {
     // FP32 denorm mode is respected, rounding mode is not. Exceptions are not supported.
     let Constraints = !if(NoDstOverlap, "@earlyclobber $vdst", "") in {