Documentation: Mark ECC as working on Sandy Bridge

Change-Id: I9f9aa5bf6ed4e1430e7067bfe5d3ce8e59e85812
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56977
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

Documentation/northbridge/intel/sandybridge/nri_features.md

@@ -84,6 +84,6 @@
 +---------------------------+----------------------+-------------+---------+---------------------+
 | **ECC support**                                                                                |
 +---------------------------+----------------------+-------------+---------+---------------------+
-|                       ECC |                  yes |          no |         |                     |
+|                       ECC |                  yes |         yes |     yes | Since coreboot 4.13 |
 +---------------------------+----------------------+-------------+---------+---------------------+
 ```