modesetting: add tile property support

This adds tiling support to the driver, it retrieves the tile info from
the kernel and translates it into the server format and exposes the
property.

(Ported from xserver commits 8fb8bbb3062f1a06621ab7030a9e89d5e8367b35
 and 6abdb54a11dac4e8854ff94ecdcb90a14321ab31)
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>