selftests/bpf: adjust OP_EQ/OP_NE handling to use subranges for branch taken

Similar to kernel-side BPF verifier logic enhancements, use 32-bit
subrange knowledge for is_branch_taken() logic in reg_bounds selftests.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231112010609.848406-9-andrii@kernel.org


Signed-off-by: Alexei Starovoitov <ast@kernel.org>