Rename EARLY_RETURN -> RESTARTABLE

This is more consistent with function and context names.
diff --git a/library/version_features.c b/library/version_features.c
index 2668eae..ec355e1 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -276,9 +276,9 @@
 #if defined(MBEDTLS_ECP_NIST_OPTIM)
     "MBEDTLS_ECP_NIST_OPTIM",
 #endif /* MBEDTLS_ECP_NIST_OPTIM */
-#if defined(MBEDTLS_ECP_EARLY_RETURN)
-    "MBEDTLS_ECP_EARLY_RETURN",
-#endif /* MBEDTLS_ECP_EARLY_RETURN */
+#if defined(MBEDTLS_ECP_RESTARTABLE)
+    "MBEDTLS_ECP_RESTARTABLE",
+#endif /* MBEDTLS_ECP_RESTARTABLE */
 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
     "MBEDTLS_ECDSA_DETERMINISTIC",
 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */