kernel: bump 6.6 to 6.6.90

kernel: bump 6.6 to 6.6.90

Remove upstreamed patches:
  bcm27xx/patches-6.6/950-0481-xhci-Use-more-event-ring-segment-table-entries.patch [1]
  pending-6.6/691-net-ipv6-fix-UDPv6-GSO-segmentation-with-NAT.patch [2]

Manually rebased patches:
  generic/hack-6.6/781-usb-net-rndis-support-asr.patch [3]

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.6.90&id=f377434945f528217e65fc5b18781caeba19ce72
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.6.90&id=e0272844995aff8cbf2cc88b78c2b35ca51eda43
[3] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.6.90&id=222b6685efe0d8c1cdb078a67bbe806f56d18f94
Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/18775
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>