rtc: rx8025: remove obsolete local_irq_disable() and local_irq_enable() for rtc_update_irq()

Since commit e6229bec

 ("rtc: make rtc_update_irq callable with irqs
enabled") rtc_update_irq() is callable with irqs enabled.

Signed-off-by: Henri Roosen <henriroosen@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>