Fix LWIP_ERROR macro - it should never be fatal (LWIP_ASSERT)

The only difference should be:
- LWIP_DEBUG enabled  -> print a diag message
- LWIP_DEBUG disabled -> NO diag message is printed

(cherry picked from commit e479bd56dfee63b96c837c54b6906b55ee5249b7)

src/include/lwip/debug.h

@@ -120,9 +120,7 @@
 #endif /* LWIP_NOASSERT */
 
 #ifndef LWIP_ERROR
-#ifndef LWIP_NOASSERT
-#define LWIP_PLATFORM_ERROR(message) LWIP_PLATFORM_ASSERT(message)
-#elif defined LWIP_DEBUG
+#ifdef LWIP_DEBUG
 #define LWIP_PLATFORM_ERROR(message) LWIP_PLATFORM_DIAG((message))
 #else
 #define LWIP_PLATFORM_ERROR(message)