fib_rules: reorder struct fib_rules fields

Move refcnt, pref, suppress_ifgroup, suppress_prefixlen out of first
cache line, as they are not used in fast path.

Make sure ctarget & fr_net are in first cache line.

(Assuming 64 bit arches and 64 bytes cache lines)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>