rtc: snvs: fix wakealarm by call enable_irq_wake earlier

When entering suspend while an wakeup alarm is set, enable_set_wake
should make sure that the RTC interrupt keep being enabled and the
.irq_set_wake for the RTC interrupt get called. However, since the
driver uses the suspend_noirq callback, the call to enable_irq_wake
has been made after disabling the interrupts. While .irq_set_wake
has been called properly, the interrupt remained disabled.

Use the suspend callback to call enable_irq_wake early enough to
ensure the RTC interrupt remains enabled.

Fixes: 7654e9d4

 ("drivers/rtc/rtc-snvs: fix suspend/resume")
Cc:  <stable@vger.kernel.org> # 3.19
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>