Você pode tentar instalar o kernel principal 4.5rc4
Executar
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.5-rc4-wily/linux-headers-4.5.0-040500rc4-generic_4.5.0-040500rc4.201602141731_amd64.deb
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.5-rc4-wily/linux-headers-4.5.0-040500rc4_4.5.0-040500rc4.201602141731_all.deb
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.5-rc4-wily/linux-image-4.5.0-040500rc4-generic_4.5.0-040500rc4.201602141731_amd64.deb
sudo dpkg -i linux*.deb
Em seguida, reinicie.
Se o touchpad ainda não funcionar, relate esse problema para o launchpad executando
ubuntu-bug linux