freedreno/ir3: limit pre-fetched tex dest

freedreno/ir3: limit pre-fetched tex dest

Teach RA to setup additional interference to prevent textures fetched
before the FS starts from ending up in a register that is too high to
encode.

Fixes mis-rendering in multiple playcanv.as webgl apps.

Note that the regression was not actually 733bee57eb8's fault, but
that was the commit that exposed the problem.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/3108
Fixes: 733bee57eb8 ("glsl: lower samplers with highp coordinates correctly")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5431>