Add NIST curves optimizations to shared mbedtls config

Author: eldiGH

pico_w/wifi/mbedtls_config_examples_common.h

@@ -68,4 +68,7 @@
 #define MBEDTLS_PEM_PARSE_C
 #define MBEDTLS_BASE64_C
 
-#endif
+// The following significantly speeds up mbedtls due to NIST optimizations.
+#define MBEDTLS_ECP_NIST_OPTIM
+
+#endif