On dunfell parts without DRM (i.MX 6 and 7) break because dri is enabled:
```
| meson.build:455:4: ERROR: Problem encountered: building dri drivers require at least one windowing system or classic osmesa
```
The break does not occur on master since dri is effectively disabled if no dri
drivers are configured. Disabling dri outright is still a better implementation
on master, and of course is required on dunfell.
Signed-off-by: Tom Hochstein <tom.hochstein@nxp.com>
