shill: netlink: Remove libgenl / libnl dependencies

shill no longer depends on libgenl / libnl in any meaningful
ways.  This CL removes the last incidental dependencies and
removes the link line for it:

  - Use of nla_total_len / nla_attr_size can be restated
    trivially using constants from linux/netlink.h.
  - The NLA_* type values no longer need to match up with
    libnl, since we don't use this for policy anymore.
    The NetlinkAttribute::Type is actually marginally more
    descriptive.
  - Remove defunct includes, references and comments.

BUG=chromium:512152
TEST=Unit tests

Change-Id: I8cb7d28f8382a0cfac0a3fe82acb1736ba321e27
Reviewed-on: https://chromium-review.googlesource.com/289236
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
1 file changed