net: Switch to skb_dstref_steal/skb_dstref_restore for ip_route_input callers

net: Switch to skb_dstref_steal/skb_dstref_restore for ip_route_input callers

Going forward skb_dst_set will assert that skb dst_entry
is empty during skb_dst_set. skb_dstref_steal is added to reset
existing entry without doing refcnt. skb_dstref_restore should
be used to restore the previous entry. Convert icmp_route_lookup
and ip_options_rcv_srr to these helpers. Add extra call to
skb_dstref_reset to icmp_route_lookup to clear the ip_route_input
entry.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250818154032.3173645-5-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>