treewide: add explicit default variant part 2

treewide: add explicit default variant part 2

Add 'DEFAULT_VARIANT' to two packages, 'iw' and 'eapol-test',
that were missed in the first pass.  Refactor 'iw' and 'ethtool'
package definitions to be consistent with the pattern used in most
other packages.

Fixes: https://github.com/openwrt/openwrt/commit/f4fdb996
Fixes: https://github.com/openwrt/openwrt/commit/7a78dc4a
Signed-off-by: Eric Fahlgren <ericfahlgren@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21380
Signed-off-by: Robert Marko <robimarko@gmail.com>