ipv4: Set offload_failed flag in fibmatch results

Due to a small omission, the offload_failed flag is missing from ipv4
fibmatch results. Make sure it is set correctly.

The issue can be witnessed using the following commands:
echo "1 1" > /sys/bus/netdevsim/new_device
ip link add dummy1 up type dummy
ip route add 192.0.2.0/24 dev dummy1
echo 1 > /sys/kernel/debug/netdevsim/netdevsim1/fib/fail_route_offload
ip route add 198.51.100.0/24 dev dummy1
ip route
	# 192.168.15.0/24 has rt_trap
	# 198.51.100.0/24 has rt_offload_failed
ip route get 192.168.15.1 fibmatch
	# Result has rt_trap
ip route get 198.51.100.1 fibmatch
	# Result differs from the route shown by `ip route`, it is missing
	# rt_offload_failed
ip link del dev dummy1
echo 1 > /sys/bus/netdevsim/del_device

Fixes: 36c5100 ("IPv4: Add "offload failed" indication to routes")
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230926182730.231208-1-bpoirier@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: gobenji

net/ipv4/route.c

@@ -3417,6 +3417,8 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
 				    fa->fa_type == fri.type) {
 					fri.offload = READ_ONCE(fa->offload);
 					fri.trap = READ_ONCE(fa->trap);
+					fri.offload_failed =
+						READ_ONCE(fa->offload_failed);
 					break;
 				}
 			}