Revert "turris1x-support: fix boot.scr location"

Even though, the previous solution fixes this output:
```
cmp: /boot/boot.scr: No such file or directory
cp: can't stat '/boot/boot.scr': No such file or directory
```

It seems there is some issue with infinite loop of symlinks
```
INFO:Executing postupdate hook: 10_kernel-install
//boot/zImage /tmp/tmp.NEAjjh/zImage differ: char 5, line 1
cmp: //boot/fdt: Symbolic link loop
cp: can't stat '//boot/fdt': Symbolic link loop
```

Because of that, revert it for now as we would like to release a new
version soon.

This reverts commit e68eda1d.