anv: set right datatypes in anv_pipeline_binding

anv: set right datatypes in anv_pipeline_binding

This structure contains two fields, binding and index, that store the
binding in the descriptor set and the index inside the binding.

These structures are defined as uint8_t, but the types in Vulkan
specification are uint32_t, so big values are clamp.

This fixes dEQP-VK.binding_model.shader_access.*.multiple_arbitrary_descriptors.*

v2: use UINT32_MAX for index when having no render targets (Tapani)

Reviewed-by: Tapani Pälli <tapani.palli@intel.com>