ARM: vexpress: Reset driver

This is a simple driver providing platform restart and power off
functions using VE config infrastructure.

By writing to the "active" attribute of the reboot or reset device,
user can decide what if the platform is supposed to execute full power
cycle (reboot, default) or simply assert system level reset signal.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>

Conflicts:

	include/linux/vexpress.h