Fix for the 51nb X62 laptop's sound chip, which isn't recognized with default settings.

Install from AUR on Arch and derivatives, for other systemd-enabled distributions, copy snd-hda-intel-x62.conf to /etc/modprobe.d/ and x62-alsa-config.service to /usr/lib/systemd/system/x62-alsa-config.service, then run systemctl enable x62-alsa-config and reboot.

Original fix by Quintus, ported over to systemd by me.