intel/isl: Add support to emit clear value address.

intel/isl: Add support to emit clear value address.

gen10 can emit the clear color by setting it on a buffer somewhere, and
then adding only the address to the surface state.

This commit add support for that on isl_surf_fill_state, and if that is
requested, skip setting the clear value itself.

v2: Add assert to make sure we are at least on gen10.

Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>