debug: replace ECDH_C symbol with key exchange one

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/debug.h b/include/mbedtls/debug.h
index 74f5d55..01d2901 100644
--- a/include/mbedtls/debug.h
+++ b/include/mbedtls/debug.h
@@ -280,7 +280,7 @@
                              const char *text, const mbedtls_x509_crt *crt);
 #endif
 
-#if defined(MBEDTLS_ECDH_C)
+#if defined(MBEDTLS_KEY_EXCHANGE_SOME_ECDH_OR_ECDHE_ANY_ENABLED)
 typedef enum {
     MBEDTLS_DEBUG_ECDH_Q,
     MBEDTLS_DEBUG_ECDH_QP,