radv: Fix a hang on CB change by adding flushes.

This workaround fixes a hang while loading a renderdoc trace for me.

Since the workload does 1 mip per cmdbuffer it is quite hard to confirm
what exactly the conditions for the hang are but this is the most
restrictive set I found and it corresponds to a workaround in AMDVLK as
well.

CC: mesa-stable
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7210>
(cherry picked from commit 4cce4d22a72bf84459ee95223cc7d1c6542617fb)
3 files changed