boot: fix pretty nasty typo

Note to self: should I ever become a black hat hacker, this is how I'd
hide a vulnerability. ;-)

(No, this one is not a vulnerability)

Follow-up for: 163d1ea5dd

src/boot/efi/boot.c

@@ -2446,7 +2446,7 @@ static void config_load_all_entries(
                                       reboot_into_firmware);
 
         if (config->entry_count == 0)
-                return
+                return;
 
         config_write_entries_to_variable(config);