kernel: bump 5.15 to 5.15.42

kernel: bump 5.15 to 5.15.42

Deleted (upstreamed):
generic/backport-5.15/610-v5.18-netfilter-flowtable-move-dst_check-to-packet-path.patch [1]
generic/pending-5.15/704-00-netfilter-flowtable-fix-excessive-hw-offload-attempt.patch [2]
generic/pending-5.15/704-01-netfilter-nft_flow_offload-skip-dst-neigh-lookup-for.patch [3]
generic/pending-5.15/704-02-net-fix-dev_fill_forward_path-with-pppoe-bridge.patch [4]
generic/pending-5.15/704-03-netfilter-nft_flow_offload-fix-offload-with-pppoe-vl.patch [5]

Manually rebased:
generic/hack-5.15/650-netfilter-add-xt_FLOWOFFLOAD-target.patch

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.42&id=88b937673b3552d54da20f648e61a123f4c1fa67
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.42&id=5f4197a020c049a59ea7907c31f9ab037dcefefe
[3] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.42&id=7613dcaceee281973145588f4244f2f78ef85b7f
[4] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.42&id=f96b2e06721249ebf8da3254cfef29dcb6583948
[5] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.42&id=b329889974aed47e1167c85653c07097013e01a7

Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>