drm/virtio: Remove restriction of non-zero blob_flags

With native userspace drivers in guest, a lot of GEM objects need to be
neither shared nor mappable.  And in fact making everything mappable
and/or sharable results in unreasonably high fd usage in host VMM.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220219170301.545432-1-robdclark@gmail.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>