ARM: dts: ux500: Bump AUX1 voltage

The voltage default on the AB8500 VAUX1 regulator is way
too low and does not correspond to the setting in the
vendor tree. This should be 2.8-3.3 V not 2.5-2.9 V or
things like the HREFP520 touchscreen will not work.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>