Update references in some test function documentation

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/include/test/random.h b/tests/include/test/random.h
index 5e7e4e6..22b9b5c 100644
--- a/tests/include/test/random.h
+++ b/tests/include/test/random.h
@@ -67,24 +67,24 @@
                                size_t len );
 
 /**
- * This function only returns zeros
+ * This function only returns zeros.
  *
- * rng_state shall be NULL.
+ * \p rng_state shall be \c NULL.
  */
 int mbedtls_test_rnd_zero_rand( void *rng_state,
                                 unsigned char *output,
                                 size_t len );
 
 /**
- * This function returns random based on a buffer it receives.
+ * This function returns random data based on a buffer it receives.
  *
- * rng_state shall be a pointer to a rnd_buf_info structure.
+ * \p rng_state shall be a pointer to a #mbedtls_test_rnd_buf_info structure.
  *
  * The number of bytes released from the buffer on each call to
  * the random function is specified by per_call. (Can be between
  * 1 and 4)
  *
- * After the buffer is empty it will return rand();
+ * After the buffer is empty it will return mbedtls_test_rnd_std_rand().
  */
 int mbedtls_test_rnd_buffer_rand( void *rng_state,
                                   unsigned char *output,
@@ -96,7 +96,7 @@
  * Pseudo random is based on the XTEA encryption algorithm to
  * generate pseudorandom.
  *
- * rng_state shall be a pointer to a rnd_pseudo_info structure.
+ * \p rng_state shall be a pointer to a #mbedtls_test_rnd_pseudo_info structure.
  */
 int mbedtls_test_rnd_pseudo_rand( void *rng_state,
                                   unsigned char *output,