Merge branch 'nh-flushing'

Ido Schimmel says:

====================
nexthop: Support large scale nexthop flushing

Patch #1 fixes a day-one bug in the nexthop code and allows "ip nexthop
flush" to work correctly with large number of nexthops that do not fit
in a single-part dump.

Patch #2 adds a test case.

Targeting at net-next since this use case never worked, the flow is
pretty obscure and such a large number of nexthops is unlikely to be
used in any real-world scenario.

Tested with fib_nexthops.sh:

Tests passed: 219
Tests failed:   0
====================

Signed-off-by: David S. Miller <davem@davemloft.net>