drivers/intel/fsp2_0: Add coreboot<->FSP header files

This adds important header files that specify calling interface between
coreboot and FSP.

Change-Id: I393601c91e3c3f630e0fc899f1140ecefed8ecba
Signed-off-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-on: https://review.coreboot.org/13796
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/drivers/intel/fsp2_0/Kconfig

@@ -0,0 +1,6 @@
+config PLATFORM_USES_FSP2_0
+	bool
+	help
+	  Include FSP 2.0 wrappers and functionality
+
+