Document that ECP_RESTARTABLE depends on ECP_C

This is not new, it had always been the case, just not documented.

Pointed out by depends.py pkalgs (again, now that restartable is part of
full).

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/scripts/depends.py b/tests/scripts/depends.py
index 0d6ec94..d09b732 100755
--- a/tests/scripts/depends.py
+++ b/tests/scripts/depends.py
@@ -234,6 +234,7 @@
     'MBEDTLS_ECP_C': ['MBEDTLS_ECDSA_C',
                       'MBEDTLS_ECDH_C',
                       'MBEDTLS_ECJPAKE_C',
+                      'MBEDTLS_ECP_RESTARTABLE',
                       'MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED',
                       'MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED',
                       'MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED',