sunxi: Drop FEL variants of defconfigs.

This can now be configured via Kconfig, e.g. with:

    $ make BOARD_defconfig
    $ echo CONFIG_SPL_FEL=y >> .config
    $ echo CONFIG_SPL_FEL=y >> spl/.config

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>