genX/state: Set CubeSurfaceControlMode to OVERRIDE

genX/state: Set CubeSurfaceControlMode to OVERRIDE

This makes it act like the address mode is set to TEXCOORDMODE_CUBE
whenever this sampler is combined with a cube surface.  This *should* be
what we need for Vulkan.  Interestingly, the PRM contains a programming
note for this field that says simply, "This field must be set to
CUBECTRLMODE_PROGRAMMED".  However, emprical evidence suggests that it does
what the PRM says it does and OVERRIDE is just fine.