Guard the tinycrypt code with MBEDTLS_USE_TINYCRYPT

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/tinycrypt/ecc_dh.c b/tinycrypt/ecc_dh.c
index 6285cf3..b6b1898 100644
--- a/tinycrypt/ecc_dh.c
+++ b/tinycrypt/ecc_dh.c
@@ -66,6 +66,7 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
+#if defined(MBEDTLS_USE_TINYCRYPT)
 #include <tinycrypt/ecc.h>
 #include <tinycrypt/ecc_dh.h>
 #include <string.h>
@@ -195,3 +196,4 @@
 
 	return UECC_FAULT_DETECTED;
 }
+#endif /* MBEDTLS_USE_TINYCRYPT */