Merge branch 'sock_map: clean up and refactor code for BPF_SK_SKB_VERDICT'

Cong Wang says:

====================

From: Cong Wang <cong.wang@bytedance.com>

This patchset is the first series of patches separated out from
the original large patchset, to make reviews easier. This patchset
does not add any new feature or change any functionality but merely
cleans up the existing sockmap and skmsg code and refactors it, to
prepare for the patches followed up. This passed all BPF selftests.

To see the big picture, the original whole patchset is available
on github: https://github.com/congwang/linux/tree/sockmap

and this patchset is also available on github:
https://github.com/congwang/linux/tree/sockmap1
---
v7: add 1 trivial cleanup patch
    define a mask for sk_redir
    fix CONFIG_BPF_SYSCALL in include/net/udp.h
    make sk_psock_done_strp() static
    move skb_bpf_redirect_clear() to sk_psock_backlog()

v6: fix !CONFIG_INET case

v5: improve CONFIG_BPF_SYSCALL dependency
    add 3 trivial cleanup patches

v4: reuse skb dst instead of skb ext
    fix another Kconfig error

v3: fix a few Kconfig compile errors
    remove an unused variable
    add a comment for bpf_convert_data_end_access()

v2: split the original patchset
    compute data_end with bpf_convert_data_end_access()
    get rid of psock->bpf_running
    reduce the scope of CONFIG_BPF_STREAM_PARSER
    do not add CONFIG_BPF_SOCK_MAP
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>