Mention validate_params does primality tests only if  GENPRIME def'd
@@ -161,11 +161,12 @@ int mbedtls_rsa_deduce_crt( const mbedtls_mpi *P, const mbedtls_mpi *Q,
* \return
* - 0 if the following conditions are satisfied
* if all relevant parameters are provided:
- * - P prime if f_rng != NULL
- * - Q prime if f_rng != NULL
+ * - P prime if f_rng != NULL (%)
+ * - Q prime if f_rng != NULL (%)
* - 1 < N = P * Q
* - 1 < D, E < N
* - D and E are modular inverses modulo P-1 and Q-1
+ * (%) This is only done if MBEDTLS_GENPRIME is defined.
* - A non-zero error code otherwise.
*
* \note The function can be used with a restricted set of arguments
