nb/intel/sandybridge: Reserve CAR region with !NATIVE_RAMINIT

Fail builds if MRC blobs pool heap would get corrupted
by CAR relocatable data from coreboot proper.

Add runtime logging how much pool was required.

Change-Id: Ibc771b592b35d77be81fce87769314fe6bb84c87
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31150
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/x86/car.ld

@@ -85,6 +85,14 @@
 	_car_global_end = .;
 	_car_relocatable_data_end = .;
 
+#if IS_ENABLED(CONFIG_NORTHBRIDGE_INTEL_SANDYBRIDGE) && \
+    !IS_ENABLED(CONFIG_USE_NATIVE_RAMINIT)
+	. = ABSOLUTE(0xff7e1000);
+	_mrc_pool = .;
+	. += 0x5000;
+	_emrc_pool = .;
+#endif
+
 #if !IS_ENABLED(CONFIG_C_ENVIRONMENT_BOOTBLOCK)
 	_car_stack_start = .;
 	_car_stack_end = _car_region_end;