HARDWARE.md: Add Asus X554L
As requested on the chat. Full hardware status of my Asus X554L:
- UEFI boot broken, BIOS boot works.
- Correct graphics modes are offered.
- Touchpad works.
- Keyboard including multimedia keys are working.
- Wired networking slow but works. (RTL8168)
- Audio doesn't work,
ihdad
complains about no output pins. - DOOM runs.
Edited by Nagy Tibor