ipv4: remove unused field in struct flowi (include/net/flow.h).

This patch removes an unused field (flags) from struct flowi; it seems
that this "flags" field was used once in the past for multipath
routing with FLOWI_FLAG_MULTIPATHOLDROUTE flag (which does no longer
exist); however, the "flags" field of struct flowi is not used
anymore.

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>