st/nir: fix atomic lowering for gallium drivers

i965 and gallium handle the atomic buffer index differently. It was
just by luck that the single piglit test for this was passing.

For gallium we use the atomic binding so that we match the handling
in st_bind_atomics().

On radeonsi this fixes the CTS test:
KHR-GL43.shader_storage_buffer_object.advanced-write-fragment

It also fixes tressfx hair rendering in Tomb Raider.

Reviewed-by: Marek Olšák  <marek.olsak@amd.com>

src/compiler/nir/nir.h

@@ -2710,7 +2710,8 @@ typedef struct nir_lower_bitmap_options {
 void nir_lower_bitmap(nir_shader *shader, const nir_lower_bitmap_options *options);
 
 bool nir_lower_atomics(nir_shader *shader,
-                       const struct gl_shader_program *shader_program);
+                       const struct gl_shader_program *shader_program,
+                       bool use_binding_as_idx);
 bool nir_lower_atomics_to_ssbo(nir_shader *shader, unsigned ssbo_offset);
 bool nir_lower_to_source_mods(nir_shader *shader);