UPSTREAM: arch/x86: Share storage data structures between early stages

Define a common area in CAR so that the storage data structures can be
shared between stages.

TEST=Build and run on Reef

Change-Id: I300059af6ef55d777eb9606c88f0a7f91d024b0c
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 43d0d0d1f4
Original-Change-Id: I20a01b850a31df9887a428bf07ca476c8410d33e
Original-Signed-off-by: Lee Leahy <Leroy.P.Leahy@intel.com>
Original-Reviewed-on: https://review.coreboot.org/19300
Original-Tested-by: build bot (Jenkins)
Original-Reviewed-by: Martin Roth <martinroth@google.com>
Original-Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/494046
Commit-Ready: Furquan Shaikh <furquan@chromium.org>

src/arch/x86/car.ld

@@ -44,6 +44,11 @@
 	 * to reside in the migrated area (between _car_relocatable_data_start
 	 * and _car_relocatable_data_end). */
 	TIMESTAMP(., 0x100)
+#if IS_ENABLED(CONFIG_DRIVERS_STORAGE)
+	_car_drivers_storage_start = .;
+	. += 256;
+	_car_drivers_storage_end = .;
+#endif
 	/* _car_global_start and _car_global_end provide symbols to per-stage
 	 * variables that are not shared like the timestamp and the pre-ram
 	 * cbmem console. This is useful for clearing this area on a per-stage