LinuxKPI: skbuff.h: add more (skeleton) functions used by wireless drivers

Add a dummy skb_hwtstamps() function for now, and implement
skb_mac_header(), skb_reset_mac_header(), and skb_set_mac_header().

Add a dummy implementation of skb_get_hash() until we'll hit and
implement it. Add napi_build_skb() and skb_mark_for_recycle().

Sponsored by: The FreeBSD Foundation

(cherry picked from commit 262c5e81937ff1682632f33e92c3e42bc92e5a77)
(cherry picked from commit 369264acf7d2a317383599141ab2f36ee3d2130c)
(cherry picked from commit 1213a6bea8a16dc797efea5a7ed7d6a4d7cb4675)