packages: ethtool: restore CONFLICTS
Inadvertent removal of 'CONFLICTS' breaks kconfig selection.
Restore it.
Fixes: ded99c2984b2 ("treewide: add explicit default variant part 2")
Signed-off-by: Eric Fahlgren <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/21388
Signed-off-by: Hauke Mehrtens <[email protected]>