Make bool_to_int_with_if happy

For reasons that are unclear to me, I am seeing this lint fire in
clippy_lints/src/macro_metavars_in_unsafe.rs.

clippy_lints/src/macro_metavars_in_unsafe.rs

@@ -221,7 +221,7 @@ impl<'tcx> LateLintPass<'tcx> for ExprMetavarsInUnsafe {
 
         let mut vis = BodyVisitor {
             macro_unsafe_blocks: Vec::new(),
-            expn_depth: if body.value.span.from_expansion() { 1 } else { 0 },
+            expn_depth: u32::from(body.value.span.from_expansion()),
             cx,
             lint: self,
         };