Fix lwip to compile if MBED_CONF_LWIP_DEBUG_ENABLED is defined

File features/lwipstack/lwip-sys/arch/cc.h fails to compile
with error: 'MBED_NORETURN' does not name a type.
Fix with adding correct include.

Author: Teppo Järvelin

features/lwipstack/lwip-sys/arch/cc.h

@@ -34,6 +34,7 @@
 
 #include <stdint.h>
 #include <stddef.h> /* for size_t */
+#include "mbed_toolchain.h"
 
 #if LWIP_USE_EXTERNAL_MBEDTLS
 #include "mbedtls/md5.h"