net: Fix EVENTFD kconfig selection

Since 820cd34dbb5d817bacc6cbdeade99aaa01007a5c these net components
use ZVFS_EVENTFD directly instead of thru EVENTFD.
So, let's select ZVFS_EVENTFD directly instead of indirectly
thru EVENTFD.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
3 files changed