radeon: avoid possible divide by 0 in surface manager
Some users report hitting a divide by 0 with the tile split in
certain apps. Tile_split shouldn't ever be 0 unless the surface
structure was not properly initialized. I think there may be some
cases where mesa uses an improperly initialized surface struct,
but I haven't had time to track it down.
Bug:
https://bugs.freedesktop.org/show_bug.cgi?id=72425
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>