etnaviv: add NTE support
This change enables the use of NTE instead of TE and increases the number of available samplers. This unlocks some more deqp's that are limited to the number of samplers and passes them. Like
- dEQP-GLES2.functional.uniform_api.random.22
- dEQP-GLES2.functional.uniform_api.value.assigned.by_value.render.nested_structs_arrays.sampler2D_samplerCube_vertex
- dEQP-GLES2.functional.uniform_api.value.assigned.by_pointer.render.nested_structs_arrays.sampler2D_samplerCube_vertex