Fix typos/style in doxygen documentation
diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index 7ae7d22..b52ffff 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -273,7 +273,7 @@
* \param f_rng RNG function (for signature, see note)
* \param p_rng RNG parameter
*
- * \return 0 successful, or a specific error code
+ * \return 0 if successful, or a specific error code
*
* \note f_rng may be NULL if RSA is used for signature and the
* signature is made offline (otherwise f_rng is desirable