drm/tile: expose the tile property to userspace (v3)

This takes the tiling info from the connector and
exposes it to userspace, as a blob object in a
connector property.

The contents of the blob is ABI.

v2: add property + function documentation.

v3: move property setup from previous patch.
add boilerplate + fix long line (Daniel)

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>