Added missing undef for m_len in VxWorks collision fix (#4520)

Co-authored-by: Adit Sahasrabudhe <adit.sahasrabudhe@jpl.nasa.gov>
Co-authored-by: kevin-f-ortega <kevin.f.ortega@gmail.com>

Author: budhe888

Drv/Ip/UdpSocket.hpp

@@ -26,6 +26,7 @@
 // These macros are defined somewhere in inetLib.h.
 #undef m_type
 #undef m_data
+#undef m_len
 
 #else
 #include <arpa/inet.h>