Olinuxino A10s fix dcdc3

dcdc3 on Olinuxino A10s rev A is used for DDR memory power supply and
must be 1.5V

The board locks up when initializing AXP if this voltage is set to 1.2V
as is done in the current fex.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
fex:a10: add t702a tablet

Signed-off-by: Luc Verhaegen <libv@skynet.be>