[llvm] [AMDGPU][True16][CodeGen] update isel pattern with vgpr16 for 16 bit types (PR #154875)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lld-x86_64-ubuntu-fast` running on `as-builder-4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/33/builds/22671

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/AMDGPU/fcopysign.gfx11plus.ll' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llc < /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/CodeGen/AMDGPU/fcopysign.gfx11plus.ll -mtriple=amdgcn -mcpu=gfx1100 -mattr=+real-true16 -stop-after=amdgpu-isel | /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/CodeGen/AMDGPU/fcopysign.gfx11plus.ll --check-prefixes=GFX11,GFX11-REAL16 # RUN: at line 2
+ /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/llvm/test/CodeGen/AMDGPU/fcopysign.gfx11plus.ll --check-prefixes=GFX11,GFX11-REAL16
error: no check strings found with prefix 'GFX11:'
+ /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=+real-true16 -stop-after=amdgpu-isel

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/154875