rtc: Remove 2nd reference to max6900.o in drivers/rtc/Makefile

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 9be2130..800ab99 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -43,7 +43,6 @@
 COBJS-y += m41t11.o
 COBJS-y += m41t60.o
 COBJS-$(CONFIG_RTC_M41T62) += m41t62.o
-COBJS-y += max6900.o
 COBJS-y += m48t35ax.o
 COBJS-y += max6900.o
 COBJS-y += mc146818.o