x86: Select advanced Intel code only if allowed

At present most of the Intel-specific code is built on all devices, even
those which don't have software support for the features provided there.

This means that any board can enable CONFIG_INTEL_ACPIGEN even if it does
not have the required features.

Add a new INTEL_SOC option to control this access. This must be selected
by SoCs that can support the required features.

Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: fixed a typo in arch/x86/Kconfig]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>