[ARM] pxa/mioa701: add Maxim 1586 voltage regulator

On this board, the PXA272 CPU voltage VCC_CORE is provided
by a Maxim 1586 voltage regulator. Use the regulator
framework to provide VCC_CORE control. When cpufreq will be
updated to ask for vcc_core, this will optimize power
drained by the board.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Eric Miao <eric.miao@marvell.com>