[WATCHDOG] U300 COH 901 327 watchdog driver

This patch adds support for the U300 COH 901 327 watchdog for the
U300 platform recently added to RMK:s ARM tree.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>