radv: Enable lowering dynamic quad broadcasts.

radv: Enable lowering dynamic quad broadcasts.

This will lower dynamic quad broadcasts into something that both
LLVM and ACO can understand. On hardware which supports shuffles,
they are lowered to shuffle, on older hardware (GFX6-7) they will
get lowered to constant quad broadcasts.

Fixes dEQP-VK.subgroups.quad.*.subgroupquadbroadcast_nonconst_*

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4147>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4147>