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/releases/coreboot-4.7-relnotes.md

@@ -84,7 +84,7 @@ General changes
 
 * Integrate me_cleaner
 * Add flashconsole implementation
-* Build Tianocore UEFI payload from upstream source
+* Build edk2 UEFI payload from upstream source
 * Remove CMOS NVRAM configurable baud rates
 * A common mrc_cache driver to store romstage settings in SPI flash