i965: Move all the depth/stencil/hiz offset logic into the workaround.

i965: Move all the depth/stencil/hiz offset logic into the workaround.

Given that we have the mask information here (assuming the rebase is to
the same tiling, which is safe), we can just save a set of miptrees and
offsets and the global intra-tile offset in the context and cut out a
bunch of logic.  This will also save emitting the next fix I need to do
twice.

Acked-by: Chad Versace <chad.versace@linux.intel.com>