swr: [rasterizer core] pipe renderTargetArrayIndex through to clears

swr: [rasterizer core] pipe renderTargetArrayIndex through to clears

Currently clears only operate on the 0th array index (ignoring surface
layout parameters). Instead normalize to take a RTAI like all the
load/store tile logic does, and use ComputeSurfaceAddress to properly
take the surface state's lod/array index into account.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Tim Rowley <timothy.o.rowley@intel.com>