net: Refactor inetpeer address struct

Move the inetpeer_addr_base union to inetpeer_addr and drop
inetpeer_addr_base.

Both the a6 and in6_addr overlays are not needed; drop the __be32 version
and rename in6 to a6 for consistency with ipv4. Add a new u32 array to
the union which removes the need for the typecast in the compare function
and the use of a consistent arg for both ipv4 and ipv6 addresses which
makes the compare function more readable.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>