agx: Fix tib access in internal shaders

agx: Fix tib access in internal shaders

The only case where tilebuffer access can be specially optimized is the
st_tile used in internal clear (or reload) shaders. However, other
shaders (like those used with u_blitter) may have nir->info.internal
set, so we can't key off that. Instead, add a special key for this
optimization to ensure correctness with other internal shaders.

Fixes flaky tests in dEQP-GLES2.functional.color_clear.*

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18380>