dm: fix variable argument list read without ending with va_end

va_end() was not getting called under certain condition
after the va_start() function call taking the va_list.

Tracked-On: #3406
Signed-off-by: Tianhua Sun <tianhuax.s.sun@intel.com>
Reviewed-by: Yonghua Huang <yonghua.huang@intel.com>

devicemodel/hw/platform/acpi/acpi.c

@@ -844,6 +844,7 @@ dsdt_line(const char *fmt, ...)
 	return;
 
 err_exit:
+	va_end(ap);
 	dsdt_error = -1;
 }