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>

include/mbedtls/check_config.h

@@ -124,6 +124,11 @@
 #error "MBEDTLS_ECP_RESTARTABLE defined, but it cannot coexist with an alternative ECP implementation"
 #endif
 
+#if defined(MBEDTLS_ECP_RESTARTABLE)           && \
+    !defined(MBEDTLS_ECP_C)
+#error "MBEDTLS_ECP_RESTARTABLE defined, but not all prerequisites"
+#endif
+
 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) && !defined(MBEDTLS_HMAC_DRBG_C)
 #error "MBEDTLS_ECDSA_DETERMINISTIC defined, but not all prerequisites"
 #endif

include/mbedtls/mbedtls_config.h

@@ -723,6 +723,8 @@
  *
  * \note  This option only works for Short Weierstrass curves.
  *
+ * Requires: MBEDTLS_ECP_C
+ *
  * Uncomment this macro to enable restartable ECC computations.
  */
 //#define MBEDTLS_ECP_RESTARTABLE

tests/scripts/depends.py

@@ -234,6 +234,7 @@ REVERSE_DEPENDENCIES = {
     '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',