rtc: pcf8563: clear RTC_FEATURE_ALARM if no irq

If there is no IRQ hooked up, clear RTC_FEATURE_ALARM to make the core
ensure that userspace is made aware that alarms are not supported.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20220301131220.4011810-1-vincent.whitchurch@axis.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>