watchdog: da9063_wdt: Simplify by removing unneeded struct...

...da9063_watchdog, which contained nothing but struct watchdog_device and a
struct da9063 pointer.
Assign the struct da9063 pointer directly to the struct watchdog_device's
driver_data field instead of creating struct da9063_watchdog and assigning
it's address there.
Spares a pointer's size data memory and an indirection level in the callbacks.

Signed-off-by: Karsten Wiese <fzuuzf@googlemail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>