Cleanup misc::check_nan

This was a bit messed up after a bigger rebase.

clippy_lints/src/misc.rs

@@ -433,16 +433,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
 fn check_nan(cx: &LateContext, path: &Path, expr: &Expr) {
     if !in_constant(cx, expr.id) {
         if let Some(seg) = path.segments.last() {
-            path.segments.last().map(|seg| {
-                if seg.name == "NAN" {
-                    span_lint(
-                        cx,
-                        CMP_NAN,
-                        expr.span,
-                        "doomed comparison with NAN, use `std::{f32,f64}::is_nan()` instead",
+            if seg.name == "NAN" {
+                span_lint(
+                    cx,
+                    CMP_NAN,
+                    expr.span,
+                    "doomed comparison with NAN, use `std::{f32,f64}::is_nan()` instead",
                     );
-                }
-            });
+            }
         }
     }
 }