Add check for the ecp module variants

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/library/ecp.c b/library/ecp.c
index 1d690d1..6087256 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -3639,6 +3639,16 @@
 
 #endif /* MBEDTLS_SELF_TEST */
 
+#if defined(MBEDTLS_TEST_HOOKS)
+
+MBEDTLS_STATIC_TESTABLE
+mbedtls_ecp_variant mbedtls_ecp_get_variant()
+{
+    return MBEDTLS_ECP_VARIANT_WITH_MPI_STRUCT;
+}
+
+#endif /* MBEDTLS_TEST_HOOKS */
+
 #endif /* !MBEDTLS_ECP_ALT */
 
 #endif /* MBEDTLS_ECP_LIGHT */