ipv4: Correct/silence an endian warning in __ip_do_redirect

ipv4: Correct/silence an endian warning in __ip_do_redirect

net/ipv4/route.c:783:46: warning: incorrect type in argument 2 (different base types)
net/ipv4/route.c:783:46:    expected unsigned int [usertype] key
net/ipv4/route.c:783:46:    got restricted __be32 [usertype] new_gw

Fixes: 969447f226b4 ("ipv4: use new_gw for redirect neigh lookup")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Link: https://lore.kernel.org/r/20231119141759.420477-1-chentao@kylinos.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>