rtc-at91rm9200: use shadow IMR on at91sam9x5

Add support for the at91sam9x5-family which must use the shadow
interrupt mask due to a hardware issue (causing RTC_IMR to always be
zero).

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>
Cc: Robert Nelson <Robert.Nelson@digikey.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c
index 811a102..f296f3f 100644
--- a/drivers/rtc/rtc-at91rm9200.c
+++ b/drivers/rtc/rtc-at91rm9200.c
@@ -309,12 +309,19 @@
 static const struct at91_rtc_config at91rm9200_config = {
 };
 
+static const struct at91_rtc_config at91sam9x5_config = {
+	.use_shadow_imr	= true,
+};
+
 #ifdef CONFIG_OF
 static const struct of_device_id at91_rtc_dt_ids[] = {
 	{
 		.compatible = "atmel,at91rm9200-rtc",
 		.data = &at91rm9200_config,
 	}, {
+		.compatible = "atmel,at91sam9x5-rtc",
+		.data = &at91sam9x5_config,
+	}, {
 		/* sentinel */
 	}
 };