pcf50633: Properly reenable charging when the supply conditions change

If chgmod == BATFULL, setting chgena has no effect. Datasheet says we
need to set resume instead but when autoresume is used resume doesn't
work. Clear and set chgena instead.

This enables a user to force charging by re-plugging USB even when the
charger entered Battery Full mode, might be handy before a long trip.

Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>