Revert "shader: preserve raw VCC bits in S_MOV_B64 (#418)"

This reverts commit 6758d67942.

An EXEC pair loses its mask provenance and falls into the raw high-word path. The saved all-ones high word then keeps waterfall branches true and wedges GPU work.

src/graphics/shader/recompiler/ir/IREmitter.cpp

@@ -76,14 +76,6 @@ void IREmitter::SetExec(U1 value) {
 	Emit(ValueOpcode::SetExec, {value});
 }
 
-U1 IREmitter::GetExecMaskTag() {
-	return U1(Emit(ValueOpcode::GetExecMaskTag));
-}
-
-void IREmitter::SetExecMaskTag(U1 value) {
-	Emit(ValueOpcode::SetExecMaskTag, {value});
-}
-
 U32 IREmitter::GetExecLo() {
 	return U32(Emit(ValueOpcode::GetExecLo));
 }
@@ -108,14 +100,6 @@ void IREmitter::SetVcc(U1 value) {
 	Emit(ValueOpcode::SetVcc, {value});
 }
 
-U1 IREmitter::GetVccMaskValidTag() {
-	return U1(Emit(ValueOpcode::GetVccMaskValidTag));
-}
-
-void IREmitter::SetVccMaskValidTag(U1 value) {
-	Emit(ValueOpcode::SetVccMaskValidTag, {value});
-}
-
 U32 IREmitter::GetVccLo() {
 	return U32(Emit(ValueOpcode::GetVccLo));
 }