Fix typos in C header files

Signed-off-by: Tobias Nießen <tniessen@tnie.de>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 40814e6..b9b2e04 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2496,7 +2496,7 @@
  *
  * \param conf          The SSL configuration.
  * \param prot_version  Protocol version. One of MBEDTLS_SSL_MINOR_VERSION_x macros.
- * \return              Ciphersuites pointer if succesful.
+ * \return              Ciphersuites pointer if successful.
  * \return              \c NULL if no ciphersuites where found.
  */
 const int *mbedtls_ssl_get_protocol_version_ciphersuites(
@@ -4188,7 +4188,7 @@
 /**
  * \brief          TLS-PRF function for key derivation.
  *
- * \param prf      The tls_prf type funtion type to be used.
+ * \param prf      The tls_prf type function type to be used.
  * \param secret   Secret for the key derivation function.
  * \param slen     Length of the secret.
  * \param label    String label for the key derivation function,
@@ -4198,7 +4198,7 @@
  * \param dstbuf   The buffer holding the derived key.
  * \param dlen     Length of the output buffer.
  *
- * \return         0 on sucess. An SSL specific error on failure.
+ * \return         0 on success. An SSL specific error on failure.
  */
 int  mbedtls_ssl_tls_prf( const mbedtls_tls_prf_types prf,
                           const unsigned char *secret, size_t slen,