With Mesa 21 evdi and udl displays are black

This was noticed by DisplayLink evdi driver users here: https://github.com/DisplayLink/evdi/issues/279

Issue is reproducible on Pop!_OS 20.10

In verbose drm dmesg logs there is following error:

[drm:drm_ioctl [drm]] comm="Xorg" pid=1283, dev=0xe201, auth=1, DRM_IOCTL_MODE_ADDFB
[drm:framebuffer_check [drm]] no buffer object handle for plane 0
[drm:drm_ioctl [drm]] comm="Xorg", pid=1283, ret=-22

And in Xorg.log

[    21.874] (II) modeset(0): Modeline "1920x1080"x0.0  152.84  1920 2000 2060 2250  1080 1086 1094 1132 -hsync -vsync (67.9 kHz eP)
[    22.081] failed to add fb -22

After investigation and some debugging we have found out that Mesa 21.0.0 is trigering that issue.