agx: Switch to scoped_barrier

agx: Switch to scoped_barrier

Rather than ingesting separate control and memory barriers, ingest only the
combined and optimized scoped_barrier intrinsic. For barriers originating from
GLSL, this makes it easier to ensure correctness. For barriers originating from
SPIR-V, this is required for translation at all, as spirv_to_nir knows only
scoped barriers. So this gets us closer to Vulkan and OpenCL.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21752>