intel/isl: Tighten up restrictions for CCS on gen7
It may technically be possible to enable some sort of fast-clear support
for at least the base slice of a 2D array texture on gen7. However,
it's not documented to work, we've never tried to do it in GL, and we
have no idea what the hardware does if you turn on CCS_D with arrayed
rendering. Let's just play it safe and disallow it for now. If someone
really cares that much about gen7 performance, they can come along and
try to get it working later.