Merge branch 'tcp-rework-tcp_v-4-6-_send_check'

Eric Dumazet says:

====================
tcp: rework tcp_v{4,6}_send_check()

tcp_v{4,6}_send_check() are only called from __tcp_transmit_skb()

They currently are in different files (tcp_ipv4.c and tcp_ipv6.c)
thus out of line.

This series move them close to their caller so that compiler
can inline them.

For all patches in the series:

$ scripts/bloat-o-meter -t vmlinux.0 vmlinux.3
add/remove: 0/2 grow/shrink: 1/3 up/down: 102/-178 (-76)
Function                                     old     new   delta
__tcp_transmit_skb                          3321    3423    +102
tcp_v4_send_check                            136     132      -4
__tcp_v4_send_check                          130     121      -9
mptcp_subflow_init                           777     763     -14
__pfx_tcp_v6_send_check                       16       -     -16
tcp_v6_send_check                            135       -    -135
Total: Before=25143100, After=25143024, chg -0.00%
====================

Link: https://patch.msgid.link/20260223100729.3761597-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>