fib, fib6: reject invalid feature bits

Feature bits that are invalid should not be accepted by the kernel,
only the lower 4 bits may be configured, but not the remaining ones.
Even from these 4, 2 of them are unused.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/uapi/linux/rtnetlink.h
Simple merge

diff --cc net/ipv4/fib_semantics.c
Simple merge

diff --cc net/ipv6/route.c
Simple merge