[clang] [llvm] [AVR] Add support for many new AVR MCUs (PR #143914)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-armv7-lnt` running on `linaro-clang-armv7-lnt` while building `clang,llvm` at step 6 "build stage 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/77/builds/13509

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (build stage 1) failure: 'ninja' (failure)
[1/171] Generating VCSRevision.h
[2/171] Building AVRGenAsmMatcher.inc...
FAILED: lib/Target/AVR/AVRGenAsmMatcher.inc /home/tcwg-buildbot/worker/clang-armv7-lnt/stage1/lib/Target/AVR/AVRGenAsmMatcher.inc 
cd /home/tcwg-buildbot/worker/clang-armv7-lnt/stage1/lib/Target/AVR && /home/tcwg-buildbot/worker/clang-armv7-lnt/stage1/bin/llvm-tblgen -gen-asm-matcher -I /home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm/lib/Target/AVR -I/home/tcwg-buildbot/worker/clang-armv7-lnt/stage1/include -I/home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm/include -I /home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm/lib/Target /home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm/lib/Target/AVR/AVR.td --write-if-changed -o AVRGenAsmMatcher.inc -d AVRGenAsmMatcher.inc.d && /usr/local/bin/cmake -E cmake_transform_depfile Ninja gccdepfile /home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm /home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm/lib/Target/AVR /home/tcwg-buildbot/worker/clang-armv7-lnt/stage1 /home/tcwg-buildbot/worker/clang-armv7-lnt/stage1/lib/Target/AVR /home/tcwg-buildbot/worker/clang-armv7-lnt/stage1/lib/Target/AVR/AVRGenAsmMatcher.inc.d /home/tcwg-buildbot/worker/clang-armv7-lnt/stage1/CMakeFiles/d/96a45b5b943d07d04318823904bae9c88721d7e6adf99d0c766d92a33ddfc324.d
Included from /home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm/lib/Target/AVR/AVR.td:21:
/home/tcwg-buildbot/worker/clang-armv7-lnt/llvm/llvm/lib/Target/AVR/AVRDevices.td:591:27: error: Variable not defined: 'FamilyXMEGA2'
def : Device<"avr64da28", FamilyXMEGA2, ELFArchXMEGA2>;
                          ^
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/143914