panvk: refactor panvk_queue_submit
What does this MR do and why?
I am working on u_trace
support in my wip panvk-utrace branch. I realized that it makes panvk_queue_submit
much more complex and it is better to refactor panvk_queue_submit
first.
This MR refactors panvk_queue_submit
piece by piece. Each commit should be small enough and reviewable.
Most commits have no functional change. The only two exceptions are noted in the commit message (panvk_queue_submit_init_storage does not reserve for signal_ops unconditionally; pandecode_next_frame is called earlier).