x86: sandbox: Add missing PCI bar to barinfo

There are expecte to be bars 0 through 5, but the last of these was
missing leading to an read beyond the buffer. Add the missing element
with zero values.

Signed-off-by: Andrew Scull <ascull@google.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>