rtc: fsl-ftm-alarm: report alarm to core

Report interrupt state to the RTC core.

Signed-off-by: Biwen Li <biwen.li@nxp.com>
Link: https://lore.kernel.org/r/20200327084457.45161-1-biwen.li@nxp.com


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