Add missing dependencies for ECDH_xxx key exchanges

ECDH_ECDSA requires ECDSA and ECDH_RSA requires RSA.

Signed-off-by: Gilles Peskine <gilles.peskine@arm.com>
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 0bab0c0..24ba789 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1085,7 +1085,7 @@
  *
  * Enable the ECDH-ECDSA based ciphersuite modes in SSL / TLS.
  *
- * Requires: MBEDTLS_ECDH_C, MBEDTLS_X509_CRT_PARSE_C
+ * Requires: MBEDTLS_ECDH_C, MBEDTLS_ECDSA_C, MBEDTLS_X509_CRT_PARSE_C
  *
  * This enables the following ciphersuites (if other requisites are
  * enabled as well):
@@ -1109,7 +1109,7 @@
  *
  * Enable the ECDH-RSA based ciphersuite modes in SSL / TLS.
  *
- * Requires: MBEDTLS_ECDH_C, MBEDTLS_X509_CRT_PARSE_C
+ * Requires: MBEDTLS_ECDH_C, MBEDTLS_RSA_C, MBEDTLS_X509_CRT_PARSE_C
  *
  * This enables the following ciphersuites (if other requisites are
  * enabled as well):