cheza: Wrap FMAP sections with calibration data in RO_PRESERVE section

The Cheza board contains a couple of non-standard FMAP sections that
contain per-board calibration data. When flashing new firmware to the
board, care should be taken to copy these sections over so that all
features can still function correctly afterwards. This patch wraps a new
RO_PRESERVE FMAP section around these sections to make them easier to
preserve as a group.

Change-Id: I77919336f609a1be399598736f46921c3da99e68
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/28728
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: T Michael Turney <mturney@codeaurora.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

src/mainboard/google/cheza/chromeos.fmd

@@ -24,8 +24,10 @@ FLASH@0x0 8M {
 			RO_FRID 0x100
 		}
 		RO_VPD 16K
-		RO_DDR_TRAINING 8K
-		RO_FSG
+		RO_PRESERVE {
+			RO_DDR_TRAINING 8K
+			RO_FSG
+		}
 	}
 
 	RW_VPD 32K