drivers/intel/fsp2_0: add option to incorporate platform memory version

On Chrome OS systems a memory setting change is needed to be deployed
without updating the FSP blob proper. Under such conditions one needs
to trigger retrain of the memory. For ease of use provide an option,
FSP_PLATFORM_MEMORY_SETTINGS_VERSIONS, which incorproates the SoC
and mainboard memory setting version number into the FSP version
passed to the platform. The lower 8 bits of the FSP version are the
build number which in practice is normally 0. Use those 8 bits to
include the SoC and mainboard memory settings version. When FSP,
SoC, or mainboard memory setting number is bumped a retrain will be
triggered.

BUG=b:37687843

Change-Id: I6a269dcf654be7a409045cedeea3f82eb641f1d6
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/19452
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

src/drivers/intel/fsp2_0/Kconfig

@@ -118,4 +118,12 @@ config FSP2_0_USES_TPM_MRC_HASH
 	default n
 	select VBOOT_HAS_REC_HASH_SPACE
 
+config FSP_PLATFORM_MEMORY_SETTINGS_VERSIONS
+	bool
+	help
+	  This is selected by SoC or mainboard to supply their own
+	  concept of a version for the memory settings respectively.
+	  This allows deployed systems to bump their version number
+	  with the same FSP which will trigger a retrain of the memory.
+
 endif