Add support for the x-powers axp209 pmic which is found on most A10, A13 and
A20 boards.

And enable AXP209 support for the Cubietruck and Cubieboard boards.

Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>