rtc: ds1685: passing bogus values to irq_restore

We call spin_lock_irqrestore with "flags" set to zero instead of to the
value from spin_lock_irqsave().

Fixes: aaaf5fbf

 ('rtc: add driver for DS1685 family of real time clocks')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>