watchdog: da9055_wdt: Drop reference counting

Reference counting is now implemented in the watchdog core and no longer
required in watchdog drivers.

Since it was implememented a no-op, and since the local memory is allocated
with devm_kzalloc(), the reference counting code in the driver really did
not really work anyway, and this patch effectively fixes a bug which could
cause a crash on unloading if the watchdog device was still open.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>