drm/vgem: Set unique to "vgem"

drm/vgem: Set unique to "vgem"

commit fa2f97dd33c2c32a06a5ea7f6e87af06a2e26baa upstream.

Since there's only one global instance ever we don't need to have
anything fancy. Stops a WARNING in the get_unique ioctl that the
unique name isn't set.

Reportedy-and-tested-by: Fabio Coatti <fabio.coatti@gmail.com>
Cc: Fabio Coatti <fabio.coatti@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>