i965/gen8: Surface state overriding for stencil

i965/gen8: Surface state overriding for stencil

v2: Allow hardware to offset accesses to individual layers. Also leave
    the mip-level overriding for the creator of the intel renderbuffer
    to handle. Merged with "i965/gen8: Allow stencil buffers to be
    configured as single sampled"

Ken: I left the "_mesa_problem()" still in place. I think it is clearer
     to remove it in a separate patch.

Cc: "10.2" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>