Merge branch 'net-remove-some-skb_mac_header-assumptions'

Eric Dumazet says:

====================
net: remove some skb_mac_header assumptions

Historically, we tried o maintain skb_mac_header available in most of
networking paths.

When reaching ndo_start_xmit() handlers, skb_mac_header() should always
be skb->data.

With recent additions of skb_mac_header_was_set() and
DEBUG_NET_WARN_ON_ONCE() in skb_mac_header(), we can attempt
to remove our reliance on skb_mac_header in TX paths.

When this effort completes we will remove skb_reset_mac_header()
from __dev_queue_xmit() and replace it by
skb_unset_mac_header() on DEBUG_NET builds.
====================

Link: https://lore.kernel.org/r/20230321164519.1286357-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>