mesa rendering issue on Librem 5 (screen all glitchy)
### Describe your issue
With latest Mobian images (bookworm), on the Librem 5 the screen is all glitchy (see image).
This can also be reproduced by using an old image without this issue (mesa 21.3.7-1), then upgrading the mesa packages to 22.2.0~rc1).
### Additional Information
* the TTY and splash screen do not show this issue (splash loading circle and boot logs via vol down button are devoid of glitches)
* issue persists without phosh (phoc only) so not phosh-related
* ``kmscube`` returns ``no connected connector! failed to initialize legacy DRM``
* ``kmscube -D /dev/dri/card1`` returns some Mesa/OpenGL info, then ``failed to set mode: Permission denied``
Because the TTY is fine and it's not phosh-related, a mesa issue is suspected (now confirmed).
Result from ``dmesg | grep "drm\|vga\|gpu\|dsi\|dri" -w``:
```
[ 0.150223] platform 30a00000.mipi-dsi: Fixing up cyclic dependency with 30320000.lcd-controller
[ 3.039081] etnaviv etnaviv: bound 38000000.gpu (ops 0xffff800008bb2f68)
[ 3.045809] etnaviv-gpu 38000000.gpu: model: GC7000, revision: 6214
[ 3.054061] [drm] Initialized etnaviv 1.3.0 20151214 for etnaviv on minor 0
[ 3.080973] nwl-dsi 30a00000.mipi-dsi: [drm:nwl_dsi_probe] Using LCDIF as input source
[ 3.103477] led-backlight backlight-dsi: Not enough levels defined
[ 3.110087] nwl-dsi 30a00000.mipi-dsi: [drm:nwl_dsi_host_attach] lanes=4, format=0x0 flags=0x7
[ 3.118719] panel-mantix-mlaf057we51 30a00000.mipi-dsi.0: 720x1440@63 24bpp dsi 4dl - ready
[ 3.128853] [drm] Initialized mxsfb-drm 1.0.0 20160824 for 30320000.lcd-controller on minor 1
[ 3.373996] mxsfb 30320000.lcd-controller: [drm] fb0: mxsfb-drmdrmfb frame buffer device
[ 9.636376] systemd[1]: Starting Load Kernel Module drm...
[ 9.804763] systemd[1]: modprobe@drm.service: Deactivated successfully.
[ 9.812157] systemd[1]: Finished Load Kernel Module drm.
[ 11.474768] cdns-mhdp-imx 32c00000.hdmi: [drm:cdns_mhdp_read_fw_version [cdns_mhdp_drmcore]] firmware version: 50d385ac
[ 11.512001] [drm] Initialized imx-dcss 1.0.0 20190917 for 32e00000.display-controller on minor 2
[ 11.522727] [drm] Connector status: 0
[ 11.528888] imx-dcss 32e00000.display-controller: [drm] Cannot find any crtc or sizes
[ 11.542558] [drm] Connector status: 0
[ 11.542604] imx-dcss 32e00000.display-controller: [drm] Cannot find any crtc or sizes
[ 11.554239] [drm] Connector status: 0
[ 11.554298] imx-dcss 32e00000.display-controller: [drm] Cannot find any crtc or sizes
[ 16.690286] [drm] Connector status: 0
```
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