i965: Push miptree tiling request into flags

i965: Push miptree tiling request into flags

With the last few patches a way was provided to influence lower layer miptree
layout and allocation decisions via flags (replacing bools). For simplicity, I
chose not to touch the tiling requests because the change was slightly less
mechanical than replacing the bools.

The goal is to organize the code so we can continue to add new parameters and
tiling types while minimizing risk to the existing code, and not having to
constantly add new function parameters.

v2: Rebased on Anuj's recent Yf/Ys changes
Fix non-msrt MCS allocation (was only happening in gen8 case before)

v3: small fix in assertion requested by Chad

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com> (v2)
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com> (v2)
Reviewed-by: Chad Versace <chad.versace@intel.com> (v2)