[llvm] [SPARC] Add TTI implementation for getPopcntSupport (PR #178843)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-test-suite` running on `ppc64le-clang-test-suite` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/95/builds/20023

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

```
Step 6 (test-build-unified-tree-check-all) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
PASS: lit :: verbosity.py (106505 of 106523)
PASS: lit :: shtest-shell.py (106506 of 106523)
PASS: UBSan-AddressSanitizer-powerpc64le :: TestCases/ImplicitConversion/unsigned-integer-truncation-ignorelist.c (106507 of 106523)
PASS: UBSan-ThreadSanitizer-powerpc64le :: TestCases/ImplicitConversion/signed-integer-truncation-ignorelist.c (106508 of 106523)
PASS: SanitizerCommon-tsan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (106509 of 106523)
PASS: SanitizerCommon-ubsan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (106510 of 106523)
PASS: SanitizerCommon-asan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (106511 of 106523)
PASS: SanitizerCommon-msan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (106512 of 106523)
PASS: LLVM :: CodeGen/ARM/build-attributes.ll (106513 of 106523)
PASS: mlgo-utils :: corpus/extract_ir_script.test (106514 of 106523)
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=7168.203686

```

</details>

https://github.com/llvm/llvm-project/pull/178843