ARM: 5783/1: Make it possible for U300 LDO D to shut down

This changes the regulator platform config for U300 so that the
LDO D regulator can change status and shut down the system and
the pm_shutdown() hook in regulator.c starts working.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>