net/smc: support ipv4 mapped ipv6 addr client for smc-r v2

AF_INET6 is not supported for smc-r v2 client before, even if the
ipv6 addr is ipv4 mapped. Thus, when using AF_INET6, smc-r connection
will fallback to tcp, especially for java applications running smc-r.
This patch support ipv4 mapped ipv6 addr client for smc-r v2. Clients
using real global ipv6 addr is still not supported yet.

Signed-off-by: Guangguan Wang <guangguan.wang@linux.alibaba.com>
Reviewed-by: Wen Gu <guwen@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Reviewed-by: D. Wythe <alibuda@linux.alibaba.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>