skbuff: kill skb_flow_get_ports()

Since commit a815bde5 ("net, bonding: Refactor bond_xmit_hash for use
with xdp_buff"), this function is not used anymore.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250221110941.2041629-2-nicolas.dichtel@6wind.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>