[ARM] EDMINIV2: add support for LED and power button

This patch provides standard GPIO LED control
for the ED Mini V2, with software blinking only
(CPLD hardware blinking capability is not used).

This patch also provides status of the power
button as a standard GPIO input event.

Signed-off-by: Albert Aribaud <albert.aribaud@free.fr>
Signed-off-by: Nicolas Pitre <nico@marvell.com>