bio/bss_dgram.c: harmonize usage of OPENSSL_USE_IPV6 with the rest.
bio/bss_dgram.c: harmonize usage of OPENSSL_USE_IPV6 with the rest.

Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
Reviewed-by: Kurt Roeckx <bb87b47479d83cec3c76132206933257ded727b2@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/6745)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl