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

…tomatically (sonic-net#20598)

#### Why I did it
src/sonic-linux-kernel
```
* fe78170 - (HEAD -> master, origin/master, origin/HEAD) Disable AMD memory encryption (sonic-net#438) (26 hours ago) [Samuel Angebault]
* b8cdf9e - Add arm64 dts and xmc spi device for Wistron platform support (sonic-net#433) (30 hours ago) [Owen]
```
#### How I did it
#### How to verify it
#### Description for the changelog