iris: fix global bindings and texture independent samplers for OpenCL
This is required on top of !16442 (merged) (included here) and !15811 (merged) (not included here) to make iris pass the OpenCL CTS.
This is required on top of !16442 (merged) (included here) and !15811 (merged) (not included here) to make iris pass the OpenCL CTS.