mach-ux500: provide ab8500 init vector

This adds an ab8500 regulator initialization vector for the
HREF/MOP500 series of boards. This also sets the display
regulator to be on at boot so we don't loose our splash
screen when the board comes up.

Signed-off-by: Bengt Jonsson <bengt.g.jonsson@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>