[libc][Obvious] Fix nextafter* implementation.

It broke when FPBits was converted to a union.

GitOrigin-RevId: 31ed45d9cfd5da2bf4f1d7ddba54122df6fc91fa
diff --git a/utils/FPUtil/ManipulationFunctions.h b/utils/FPUtil/ManipulationFunctions.h
index ef8a377..f0e5c8f 100644
--- a/utils/FPUtil/ManipulationFunctions.h
+++ b/utils/FPUtil/ManipulationFunctions.h
@@ -167,7 +167,7 @@
       --intVal;
     }
   } else {
-    intVal = (UIntType(toBits) & signMask) + UIntType(1);
+    intVal = (toBits.uintval() & signMask) + UIntType(1);
   }
 
   return *reinterpret_cast<T *>(&intVal);