drm: Remove entry points for legacy ioctls

DRM drivers with user-space mode setting have been removed in Linux
v6.3. [1] Now remove the ioctl entry points for these drivers. Invoking
any of the ioctl ops will unconditionally return -EINVAL to user space.
This has already been the behavior for kernels without CONFIG_DRM_LEGACY
set.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/series/111602/

 # [1]
Reviewed-by: David Airlie <airlied@gmail.com>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231122122449.11588-9-tzimmermann@suse.de