drm/panfrost: remove DRM_AUTH and respective comment

drm/panfrost: remove DRM_AUTH and respective comment

As of earlier commit we have address space separation. Yet we forgot to
remove the respective comment and DRM_AUTH in the ioctl declaration.

Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Steven Price <steven.price@arm.com>
Fixes: 7282f7645d06 ("drm/panfrost: Implement per FD address spaces")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191101130313.8862-4-emil.l.velikov@gmail.com