Remove unneeded scripts
Set the user as owner of /boot and /lib/modules

This removes the need to use sudo while compiling the kernel and nouveau
modules.
linux: remove nouveau modules after installation

Up to now we installed two versions of the nouveau module: the one that
shipped with the kernel, and the one coming from the nouveau project
itself. This led to situations where the wrong module was loaded. Remove
the linux-supplied nouveau module right after installation to avoid
this.