payloads/*/Kconfig.name: update documentation link

Old wiki is outdated for years but Kconfig help messages
of some payloads still reference it.

This commit changes those links to the corresponding page at
doc.coreboot.org.

Change-Id: I81653f1b010d8a3ac4dfc4c6ad4fa714ce5d59a1
Signed-off-by: Evgeny Zinoviev <me@ch1p.io>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/71897
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nicholas Chin <nic.c3.14@gmail.com>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>

payloads/external/LinuxBoot/Kconfig.name

@@ -8,4 +8,4 @@ config PAYLOAD_LINUXBOOT
 	  with a LinuxBoot payload. If you don't know what this is
 	  about, just leave it enabled.
 
-	  See https://coreboot.org/Payloads for more information.
+	  See https://doc.coreboot.org/payloads.html for more information.