i965: When rebasing depth or stencil, update x/y before deciding the other.

i965: When rebasing depth or stencil, update x/y before deciding the other.

Fixes a theoretical problem where we had an aligned depth buffer and a
misaligned stencil buffer with a matching tile offset, so we would fail
to rebase depth even after the needed tile offset changed due to the
rebase of stencil.

It should also fix double-rebase of a misaligned packed depth/stencil
renderbuffer, which may have been a performance issue.

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