packages/fff: Tidy up wget dependencies

The symbols BUSYBOX_CONFIG_WGET and
BUSYBOX_CONFIG_FEATURE_WGET_TIMEOUT are set in different
packages and do not correlate with where Busybox wget is
actually used.

This updates packages dependencies based on the current
situation.

Note that with current firmware, both two versions of wget
are installed:
/bin/wget
/usr/bin/wget

The latter is from busybox and is used as the default version.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Robert Langhammer <rlanghammer@web.de>
Reviewed-by: Fabian Bläse <fabian@blaese.de>