Avoid various uses of Option<Span> in favor of using DUMMY_SP in the few cases that used None

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -74,7 +74,7 @@ pub(crate) fn eval_mir_constant<'tcx>(
     let cv = fx.monomorphize(constant.const_);
     // This cannot fail because we checked all required_consts in advance.
     let val = cv
-        .eval(fx.tcx, ty::ParamEnv::reveal_all(), Some(constant.span))
+        .eval(fx.tcx, ty::ParamEnv::reveal_all(), constant.span)
         .expect("erroneous constant missed by mono item collection");
     (val, cv.ty())
 }