r300: disable PIPE_CAP_PREFER_IMM_ARRAYS_AS_CONSTBUF

r300: disable PIPE_CAP_PREFER_IMM_ARRAYS_AS_CONSTBUF

We can't do uniform buffer objects and from the hardware
perspective constants (uniforms) and immediates are treated in
the same way. They are uploaded together and fit together into the
(rather low) total constant limit. Therefore, there is actually no
advantage in converting immediates to uniforms, and a whole lot of
disadvantages (less possible optimizations and no inlining).

Fixes the dEQP regressions from https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16770

The tests failed because when there is an indirect array access the
compiler inserts a big if ladder and converting the temp to a uniform
means more instructions because the ifs cant be lowered at least
partially to selects. It is particularly visible, because the code
NIR currently emits for the indirect access doesn't really fit the
hardware, see: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6366

No change in my shader-db, so this concerns the tests only.

Signed-off-by: Pavel Ondračka <pavel.ondracka@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17576>