security/intel: Add TXT infrastructure

* Add Kconfig to enable TXT
* Add possibility to add BIOS and SINIT ACMs
* Set default BIOS ACM alignment
* Increase FIT space if TXT is enabled

The following commits depend on the basic Kconfig infrastructure.
Intel TXT isn't supported until all following commits are merged.

Change-Id: I5f0f956d2b7ba43d4e7e0062803c6d8ba569a052
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34585
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>

src/soc/intel/skylake/Kconfig

@@ -302,4 +302,8 @@ config IFD_CHIPSET
 	string
 	default "sklkbl"
 
+config INTEL_TXT_BIOSACM_ALIGNMENT
+	hex
+	default 0x40000 # 256KB
+
 endif