Make compiler happy when MBEDTLS_USE_UECC disabled
diff --git a/tinycrypt/ecc_dh.c b/tinycrypt/ecc_dh.c
index 7277879..5d0a52f 100644
--- a/tinycrypt/ecc_dh.c
+++ b/tinycrypt/ecc_dh.c
@@ -196,4 +196,6 @@
 
 	return r;
 }
+#else
+typedef int mbedtls_dummy_uecc_def;
 #endif /* MBEDTLS_USE_UECC */