Change in coreboot[master]: mb/lenovo/w541: Add Thinkpad W541

[amersel (Code Review)]

Attention is currently required from: Peter Lemenkov, Angel Pons, Alexander Couzens, Patrick Rudolph, Iru Cai (vimacs).
amersel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52659 )

Change subject: mb/lenovo/w541: Add Thinkpad W541
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Patch Set 21:

(1 comment)

Patchset:

PS20:
> Simply including the change doesn't solve the problem and it's a bit unclear how to use this.  […]

Figured out a way to enable the backlight. Using ectool as shown in this reddit post, I was able to enable and disable the backlight. This works without the addition of +51412.

https://www.reddit.com/r/coreboot/comments/eqz5xa/t440p_backlit_tester_neede...

```
low brightness
sudo ./ectool -w 0xd -z 0x42

high brightness
sudo ./ectool -w 0xd -z 0x82

disable backlight
sudo ./ectool -w 0xd -z 0x02
```