Display notch support

[Simon Ser]

> A solution to make this configuration generic and exposed by the kernel
> would standardise this across Linux

Having a KMS property for this makes sense to me.

Chatting with Jani on IRC, it doesn't seem like there's any EDID or
DisplayID block for this.

Note, Android exposes a data structure [1] with:

- Margin of the cut-out for each edge of the screen
- One rectangle per edge describing the cut-out region
- Size of the curved area for each edge of a waterfall display

I haven't found anything describing the rounded corners of the display.

[1]: https://developer.android.com/reference/android/view/DisplayCutout