drm/tegra: Remove existing framebuffer only if we support display

drm/tegra: Remove existing framebuffer only if we support display

Tegra DRM doesn't support display on Tegra234 and later, so make sure
not to remove any existing framebuffers in that case.

v2: - add comments explaining how this situation can come about
    - clear DRIVER_MODESET and DRIVER_ATOMIC feature bits

Fixes: 6848c291a54f ("drm/aperture: Convert drivers to aperture interfaces")
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240223150333.1401582-1-thierry.reding@gmail.com