Increase the Hamming distance of uECC_generate_random_int returns

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/include/tinycrypt/ecc.h b/include/tinycrypt/ecc.h
index b6fbc69..57aa508 100644
--- a/include/tinycrypt/ecc.h
+++ b/include/tinycrypt/ecc.h
@@ -155,7 +155,8 @@
  * @param random OUT -- random integer in the range 0 < random < top
  * @param top IN -- upper limit
  * @param num_words IN -- number of words
- * @return a random integer in the range 0 < random < top
+ * @return UECC_SUCCESS in case of success
+ * @return UECC_FAILURE upon failure
  */
 int uECC_generate_random_int(uECC_word_t *random, const uECC_word_t *top,
 			     wordcount_t num_words);