bio/b_print.c: drop dependency on BN config.

This might seem controversial, but it doesn't actually affect anything.
Or rather it doesn't make worse cases when it was problematic [with code
additions to 1.1.0]. One of such rare cases is 32-bit PA-RISC target
with *vendor* compiler.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3148)