[submodule] Update submodule sonic-linux-kernel to the latest HEAD au…

…tomatically (#18588)

#### Why I did it
src/sonic-linux-kernel
```
* 38bb387 - (HEAD -> master, origin/master, origin/HEAD) Update reference build to be used for kconfig diff (#392) (4 days ago) [Vivek]
```
#### How I did it
#### How to verify it
#### Description for the changelog