i965: Set "Shader Channel Select" fields in Haswell's SURFACE_STATE.

i965: Set "Shader Channel Select" fields in Haswell's SURFACE_STATE.

These can be used to implement EXT_texture_swizzle without baking
state-dependent swizzle instructions into the shader and forcing
recompiles.

For now, just set them to pass-through mode, so everything continues to
work as it did on Ivybridge.  We can optimize this later.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>