mb/google/rex/var/karis: Update fw_config KB_TYPE field

Update element "KB_TYPE_CA" for align fw_config.
Only EC will reference KB_TYPE field in fw_config. This
CL is just for align fw_config.

BUG=none
TEST=emerge coreboot pass

Change-Id: Ied54f78dddd9dddca1272fc31c9502fc11c61dde
Signed-off-by: Tyler Wang <tyler.wang@quanta.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80331
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Eran Mitrani <mitrani@google.com>

src/mainboard/google/rex/variants/karis/overridetree.cb

@@ -24,6 +24,7 @@ fw_config
 	end
 	field KB_TYPE 12
 		option KB_TYPE_DEFAULT		0
+		option KB_TYPE_CA			1
 	end
 	field WIFI_TYPE 13
 		option WIFI_CNVI		0