i965/blorp: Stop using the miptree in state setup for tex/rt surfaces

i965/blorp: Stop using the miptree in state setup for tex/rt surfaces

This commit movies us from a miptree model to a surf+bo+offset model.  In
the GL driver, miptrees are almost always at the start of the bo so the
offset is zero but we don't want to always make that assumption.  In the
sort term, gen6 stencil and HiZ will be at an offset but, in the long term,
any Vulkan surface is liable to be at a non-zero offset.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>