bpf: remove redundant s{32,64} -> u{32,64} deduction logic

bpf: remove redundant s{32,64} -> u{32,64} deduction logic

Equivalent checks were recently added in more succinct and, arguably,
safer form in:
  - f188765f23a5 ("bpf: derive smin32/smax32 from umin32/umax32 bounds");
  - 2e74aef782d3 ("bpf: derive smin/smax from umin/max bounds").

The checks we are removing in this patch set do similar checks to detect
if entire u32/u64 range has signed bit set or not set, but does it with
two separate checks.

Further, we forcefully overwrite either smin or smax (and 32-bit equvalents)
without applying normal min/max intersection logic. It's not clear why
that would be correct in all cases and seems to work by accident. This
logic is also "gated" by previous signed -> unsigned derivation, which
returns early.

All this is quite confusing and seems error-prone, while we already have
at least equivalent checks happening earlier. So remove this duplicate
and error-prone logic to simplify things a bit.

Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231112010609.848406-6-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>