watchdog: dw_wdt: Add __user annotation

Added __user annotation to fix the following sparse warnings.

drivers/watchdog/dw_wdt.c:206:38: warning: incorrect type in argument 1 (different address spaces)
drivers/watchdog/dw_wdt.c:206:38:    expected void [noderef] <asn:1>*to
drivers/watchdog/dw_wdt.c:206:38:    got struct watchdog_info *<noident>
drivers/watchdog/dw_wdt.c:211:24: warning: incorrect type in initializer (different address spaces)
drivers/watchdog/dw_wdt.c:211:24:    expected int const [noderef] <asn:1>*register __p
drivers/watchdog/dw_wdt.c:211:24:    got int *<noident>

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Jamie Iles <jamie@jamieiles.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>