Documentation: Add deprecation notice for SAR support in VPD

This change updates the release notes for coreboot-4.14 to add
deprecation notice for SAR support in VPD for Chrome OS platforms.

BUG=b:173465272

Change-Id: If6d511a22a3a2a31671dac91e57e801134d4ecf8
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51486
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/releases/coreboot-4.14-relnotes.md

@@ -10,6 +10,30 @@ Update this document with changes that should be in the release notes.
 * The chip and board additions and removals will be updated right
   before the release, so those do not need to be added.
 
+Deprecations
+------------
+
+### SAR support in VPD for Chrome OS
+
+SAR support in VPD has been deprecated for Chrome OS platforms for > 1
+year now. All new Chrome OS platforms have switched to using SAR
+tables from CBFS. For the next release, coreboot is updated to align
+with the Chrome OS factory changes and hence SAR support in VPD is
+deprecated in [CB:51483](https://review.coreboot.org/51483). Starting
+with this release, anyone building coreboot for an already released
+Chrome OS platform with SAR table in VPD will have to extract the
+"wifi_sar" key from VPD and add it as a file to CBFS using following
+steps:
+ * On DUT, read SAR value using `vpd -i RO_VPD -g wifi_sar`
+ * In coreboot repo, generate CBFS SAR file using:
+    `echo ${SAR_STRING} > site-local/${BOARD}-sar.hex`
+ * Add to site-local/Kconfig:
+    ```
+     config WIFI_SAR_CBFS_FILEPATH
+       string
+       default "site-local/${BOARD}-sar.hex"
+    ```
+
 Significant changes
 -------------------