i965/rbc: Consult rb settings for texture surface setup

i965/rbc: Consult rb settings for texture surface setup

Once mcs buffer gets allocated without delay for lossless
compression (same as we do for msaa), one gets regression in:

GL45-CTS.texture_barrier_ARB.same-texel-rw

Setting the auxiliary surface for both sampling engine and data
port seems to fix this. I haven't found any hardware documentation
backing this though.

v2 (Jason): Prepare also for the case where surface is sampled with
            non-compressible format forcing also rendering without
            compression.
v3: Split asserts and decision making.
v4: Detailed comment provided by Jason explaining the need for using
    auxiliary buffer for texturing when the same surface is also
    used as render target.
    Added check for existence of renderbuffer before considering if
    underlying miptree matches.

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>