knownhosts: Use SSH_BUFFER_FREE()

Fixes T183

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

src/knownhosts.c

@@ -129,8 +129,8 @@ static int match_hashed_hostname(const char *host, const char *hashed_host)
 
 error:
     free(hashed);
-    ssh_buffer_free(salt);
+    SSH_BUFFER_FREE(salt);
-    ssh_buffer_free(hash);
+    SSH_BUFFER_FREE(hash);
 
     return match;
 }