tu: Fix issues with render_pass tracepoint
What does this MR do and why?
cmd->state.attachments
was accessed out of bounds, which somehow instead
of crash caused the tracepoint to be skipped.
So with unused attachment ubwc info would look like ubwc=y--y|y
.
drawcall_bandwidth_per_sample_sum
was divided by 0 when there were no
draw calls in a renderpass.
Fixes: 1aab0fc4 ("tu: Add attachments' UBWC info to renderpass tracepoint")