x86: Reduce size of samus image

With the recent addition of ACPI generation, the image size has got beyond
its current limit.

Samus does not actually use this, nor x86 emulation for PCI ROMs, so
disable both features.

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