radv: fix bogus interaction between DGC and RT with descriptor bindings

radv: fix bogus interaction between DGC and RT with descriptor bindings

pipeline_is_dirty was never TRUE because it's emitted in the before
helper. This might fix bad interactions between DGC and RT because
they both use compute shaders and descriptor bindings need to be
re-emitted.

Found by inspection.

Cc: mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26417>
(cherry picked from commit ab6cf1592fc5c83a45709e68bceee9eb0e7d7870)