net, ethtool: Disallow leased real rxqs to be resized

net, ethtool: Disallow leased real rxqs to be resized

Similar to AF_XDP, do not allow queues in a physical netdev to be resized
by ethtool -L when they are leased. Cover channel resize paths (both
netlink and ioctl) to reject resizing when the queues would be affected.

Given we need to have different checks for RX vs TX, detangle the code into
a two-loop version rather than the range of new_combined + min(new_rx, new_tx)
to old_combined + max(old_rx, old_tx).

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260402231031.447597-5-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>