payloads/tianocore: Rename TianoCore to edk2

coreboot uses TianoCore interchangeably with EDK II, and whilst the
meaning is generally clear, it's not the payload it uses. EDK II is
commonly written as edk2.

coreboot builds edk2 directly from the edk2 repository. Whilst it
can build some components from edk2-platforms, the target is still
edk2.

[1] tianocore.org - "Welcome to TianoCore, the community supporting"
[2] tianocore.org - "EDK II is a modern, feature-rich, cross-platform
firmware development environment for the UEFI and UEFI Platform
Initialization (PI) specifications."

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Change-Id: I4de125d92ae38ff8dfd0c4c06806c2d2921945ab
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65820
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

Documentation/payloads.md

@@ -23,13 +23,11 @@ When chainloaded from GRUB2, the following menuentry could be used:
         module /vgaroms/seavgabios.bin
     }
 
-## Tianocore
+## edk2
 
-[Tianocore](https://www.tianocore.org) is the open source reference
-implementation of the UEFI Specifications that modern firmware for PCs is
-based on. There were various projects in the past to make it suitable as a
-coreboot payload, but these days this function is available directly in the
-UefiPayloadPkg part of its source tree.
+[edk2](https://github.com/tianocore/tianocore.github.io/wiki/Getting-Started-with-EDK-II) is an open-source modern, feature-rich,
+cross-platform firmware development environment for the UEFI and UEFI
+Platform Initialization (PI) specifications. 
 
 ## GRUB2