i965/fs: Import image memory offset calculation code.

Define a function to calculate the memory address of the image
location given by a vector of coordinates.  This is required in cases
where we need to fall back to untyped surface access, which take a raw
memory offset and know nothing about surface coordinates, type
conversion or memory tiling and swizzling.  They are still useful
because typed surface reads don't support any 64 or 128-bit formats on
IVB, and they don't support any 128-bit formats on HSW and BDW.

The tiling algorithm is implemented based on a number of parameters
which are passed in as uniforms and determine whether the surface
layout is X-tiled, Y-tiled or untiled.  This allows binding surfaces
of different tiling layouts to the pipeline without recompiling the
program.

v2: Drop VEC4 suport.
v3: Rebase.
v4: Add plenty of comments (Jason).

Reviewed-by: Jason Ekstrand <[email protected]>

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