[201911][sonic-linux-kernel] submodule update

```
23fc702 [201911][patch] mlxsw: i2c: Prevent transaction execution for special chip st (sonic-net#278)
e4f44e4 [201911] Increase log buf len size to 1M (sonic-net#265)
ef6abe3 [201911] Apply kernel patches to fix emmc unreliability (sonic-net#264)
7458347 [201911] Increase log buf len size to 1M
4edf1b4 [201911] Apply kernel patches to fix emmc unreliability
```

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>