Add IRCONV_NONE for pass-through INT to I64/U64 type change.

src/lj_asm_arm64.h

@@ -602,7 +602,7 @@ static void asm_conv(ASMState *as, IRIns *ir)
 	emit_dn(as, A64I_SXTW, dest, left);
       }
     } else {
-      if (st64) {
+      if (st64 && !(ir->op2 & IRCONV_NONE)) {
 	/* This is either a 32 bit reg/reg mov which zeroes the hiword
 	** or a load of the loword from a 64 bit address.
 	*/