ANDROID: GKI: fix crc issue in include/net/addrconf.h

In commit 97275e47 ("net: ipv6: support reporting otherwise unknown
prefix flags in RTM_NEWPREFIX") a union is added to fix some issues, but
that messes with the crc of a number of networking symbols for obvious
reasons.  As this does not actually change the abi at all, use some
GENKSYMS magic #define logic to preserve the crc so that all is well.

Updates the .xml file with the following structure change that is
abi-safe:
type 'struct prefix_info' changed
  member 'union { __u8 flags; struct { __u8 reserved; __u8 autoconf; __u8 onlink; }; }' was added
  member '__u8 reserved' was removed
  member '__u8 autoconf' was removed
  member '__u8 onlink' was removed

Bug: 161946584
Fixes: 97275e47 ("net: ipv6: support reporting otherwise unknown prefix flags in RTM_NEWPREFIX")
Cc: Maciej Żenczykowski <maze@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Change-Id: I9d2df74e8f3ae60425534f1b33d50b2bc444f7f5
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>