cpu/x86/smm: Add PCI resource store functionality

In certain cases data within protected memmory areas like SMRAM could
be leaked or modified if an attacker remaps PCI BARs to point within
that area. Add support to the existing SMM runtime to allow storing
PCI resources in SMRAM and then later retrieving them.

BRANCH=guybrush
BUG=b:186792595
TEST=builds

Signed-off-by: Robert Zieba <robertzieba@google.com>
Change-Id: I23fb1e935dd1b89f1cc5c834cc2025f0fe5fda37
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67931
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/include/device/pci_def.h

@@ -590,4 +590,8 @@
 #define PCI_DEV2DEVFN(sdev)		(((sdev)>>12) & 0xff)
 #define PCI_DEV2SEGBUS(sdev)	(((sdev)>>20) & 0xfff)
 
+/* Fields from within the device's class value. */
+#define PCI_CLASS_GET_DEVICE(c) (c >> 8)
+#define PCI_CLASS_GET_PROG(c) (c & 0xff)
+
 #endif /* PCI_DEF_H */