docs: update UEFI.md to reference upstream tianocore EDK2 repository
after testing the build briefly, it seems upstream tianocore EDK2 works fine,
no need for the separate cloud-hypervisor edk2 repo.
@@ -6,13 +6,15 @@ Cloud Hypervisor supports UEFI boot through the utilization of the EDK II based
To avoid any unnecessary issues, it is recommended to use Ubuntu 18.04 and its default toolset. Any other compatible Linux distribution is otherwise suitable, however it is suggested to use a temporary Docker container with Ubuntu 18.04 for a quick build on an existing Linux machine.
+Please note that nasm-2.15 is required for the build to succeed.
+
The commands below will compile an OVMF firmware suitable for Cloud Hypervisor.
```shell
sudo apt-get update
sudo apt-get install uuid-dev nasm iasl build-essential python3-distutils git
-git clone https://github.com/cloud-hypervisor/edk2 -b ch
+git clone https://github.com/tianocore/edk2
cd edk2
. edksetup.sh
git submodule update --init
