pci: Disable expansion ROM address decoding when signature check fails

We should not leave the expansion ROM address window open when there
is not a valid ROM.

Suggested-by: Matt Porter <mporter@konsulko.com>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>