Print drop reason from sk_skb_reason_drop. Catch up with kernel 6.11 changes

[DanPartelly]

This commit extracts a drop reason from sk_skb_reason_drop(), and prints it when sk_skb_drop_reason() is called.

This function was introduced in kernel v6.11-rc1. At the same time, kfree_skb_reason() became an inline helper which just calls sk_skb_reason_drop().
See: torvalds/linux@ba8de79

Summary of changes:

• bpf: teach kprobe_skb() to capture the 3rd function argument in the event map
• go: teach getKFreeSKBReasons() to cope with changes to kfree_skb_reason and introduction of sk_skb_reason_drop() in kernel
• go: teach getOutFuncName() about sk_skb_reason_drop()