insmod-sh: Allow writing to kmsg

modprobe would log errors to /dev/kmsg, need to explicit allow this.

```
avc:  denied  { write } for  comm="modprobe" name="kmsg" dev="tmpfs" ino=5 scontext=u:r:insmod-sh:s0 tcontext=u:object_r:kmsg_device:s0 tclass=chr_file permissive=0
```

Bug: 388717752
Test: DeviceBootTest#SELinuxUncheckedDenialBootTest
Change-Id: I49a3e6a9f76f20151034cb00f772247b0e9c668e
2 files changed