vk/cmd_buffer: Store the relocation list in the anv_batch_bo struct

vk/cmd_buffer: Store the relocation list in the anv_batch_bo struct

Before, we were doing this thing where we had one big relocation list for
the whole command buffer and each subbuffer took a chunk out of it.  Now,
we store the actual relocation list in the anv_batch_bo.  This comes at the
cost of more small allocations but makes a lot of things simpler.