nir/types: Add a utility wrapper to glsl_type::sampler_index()

I think it is more accurate to call it a sampler target (?).

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

src/compiler/nir_types.cpp

@@ -150,6 +150,13 @@ glsl_get_sampler_result_type(const struct glsl_type *type)
    return (glsl_base_type)type->sampled_type;
 }
 
+unsigned
+glsl_get_sampler_target(const struct glsl_type *type)
+{
+   assert(glsl_type_is_sampler(type));
+   return type->sampler_index();
+}
+
 unsigned
 glsl_get_record_location_offset(const struct glsl_type *type,
                                 unsigned length)

src/compiler/nir_types.h

@@ -80,6 +80,7 @@ const char *glsl_get_struct_elem_name(const struct glsl_type *type,
 
 enum glsl_sampler_dim glsl_get_sampler_dim(const struct glsl_type *type);
 enum glsl_base_type glsl_get_sampler_result_type(const struct glsl_type *type);
+unsigned glsl_get_sampler_target(const struct glsl_type *type);
 
 unsigned glsl_get_record_location_offset(const struct glsl_type *type,
                                          unsigned length);