ARM: 5864/1: Implement arch_reset() in NUC900

Implement arch_reset(), reboot from shell become possible.

Signed-off-by: lijie <eltshanli@gmail.com>
Acked-by: Wan ZongShun <mcuos.com@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>