[submodule] Update submodule sonic-stp to the latest HEAD automatically (sonic-net#20959)

#### Why I did it
src/sonic-stp
```
* ea85d65 - (HEAD -> master, origin/master, origin/HEAD) [ci] Add arm64 build on PR validation. (sonic-net#41) (20 hours ago) [Xin Wang]
* 6cdf964 - fix (25 hours ago) [Shilong Liu]
* 40cd2d5 - fix (2 days ago) [Shilong Liu]
* 0bfbed4 - makefile (2 days ago) [Shilong Liu]
* 837b0ce - makefile (2 days ago) [Shilong Liu]
* 0ef306e - fix (2 days ago) [Shilong Liu]
* 859374c - fix (2 days ago) [Shilong Liu]
* 7d65161 - fix (2 days ago) [Shilong Liu]
* 6580a62 - fix (2 days ago) [Shilong Liu]
* 017f2a9 - fix (2 days ago) [Shilong Liu]
* a26b6c2 - [ci] Try building on arm agent. (2 days ago) [Shilong Liu]
```
#### How I did it
#### How to verify it
#### Description for the changelog

Author: mssonicbld