hos: update fss0 parser

- Move extra key checks in the parser
- Remove some sept leftover checks
- Update printing to reflect PK3 name (FSS0 -> FSS/PK3)

bootloader/hos/hos_config.c

@@ -262,15 +262,6 @@ static int _config_exo_cal0_writes_enable(launch_ctxt_t *ctxt, const char *value
 
 static int _config_fss(launch_ctxt_t *ctxt, const char *value)
 {
-	LIST_FOREACH_ENTRY(ini_kv_t, kv, &ctxt->cfg->kvs, link)
-	{
-		if (!strcmp("fss0experimental", kv->key))
-		{
-			ctxt->fss0_experimental = *kv->val == '1';
-			break;
-		}
-	}
-
 	return parse_fss(ctxt, value);
 }