restorecond: use strict function prototype for definition

Clang 15 starts to complain about non strict function definitions:

    user.c:172:10: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
    int start() {
             ^
              void

Signed-off-by: Christian Göttsche <[email protected]>
Reviewed-by: Daniel Burgener <[email protected]>
Acked-by: James Carter <[email protected]>

Author: cgzones

restorecond/user.c

@@ -169,7 +169,7 @@ io_channel_callback
   return TRUE;
 }
 
-int start() {
+int start(void) {
 #ifdef HAVE_DBUS
 	GDBusConnection *bus;
 	GError *err = NULL;