mksysinfo.sh: Remove _zone_net_addr_t handling.

mksysinfo.sh: Remove _zone_net_addr_t handling.

From Rainer Orth.

The recent godump changes broke Solaris 11.1+ bootstrap in
libgo: before, gen-sysinfo.so had

type _zone_net_addr_t struct { zna_family uint16; zna_plen uint16; zna_addru struct { znau_addr6 _in6_addr; }; }

which was filtered out by mksysinfo.sh due to the use of
_in6_addr.

After the change, there's now

type _zone_net_addr_t struct { zna_family uint16; zna_plen uint16; zna_addru struct { znau_addr6 [16]byte; Godump_0_align [0]uint32; }; }

instead, not filtered, but added a second time by the
_zone_net_addr_t code in mksysinfo.sh, which leads to
redefinition warnings/errors.

Simply removing the old _zone_net_addr_t fragment fixes this
and restores bootstrap.

From-SVN: r220481