rtc: at91rm9200: use of_device_get_match_data()

Use of_device_get_match_data() since all platforms should now use DT
bindings. AVR32 architecture has been removed in
commit 26202873 ("avr32: remove support for AVR32 architecture").

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/1569500132-21164-1-git-send-email-claudiu.beznea@microchip.com


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