util/prim_restart: fix util_translate_prim_restart_ib
this was broken for the indirect case if the indirect draw count or firstIndex was nonzero and also would rewrite the index buffer onto the wrong offset of the dst buffer
Fixes: 0c85d6c5 ("gallium/util: factor out primitive-restart rewriting logic") Fixes: 330d0607 ("gallium: remove pipe_index_buffer and set_index_buffer")