intel/compiler: remove gfx6 gather wa from backend.

Crocus lowers this in the frontend, they key member is still used
but reset prior to backend.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14202>

src/intel/compiler/brw_fs_nir.cpp

@@ -6282,9 +6282,6 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
    if (srcs[TEX_LOGICAL_SRC_SHADOW_C].file != BAD_FILE)
       inst->shadow_compare = true;
 
-   if (instr->op == nir_texop_tg4 && devinfo->ver == 6)
-      emit_gfx6_gather_wa(key_tex->gfx6_gather_wa[texture], dst);
-
    fs_reg nir_dest[5];
    for (unsigned i = 0; i < dest_size; i++)
       nir_dest[i] = offset(dst, bld, i);