rtc: Kconfig: remove dependency for AT91 rtc driver

This will allow to select this driver for newer SoCs.
Keep dependency on AT91 because of the use of an header
file located in include/mach directory.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

drivers/rtc/Kconfig

@@ -838,7 +838,7 @@ config RTC_DRV_AT32AP700X
 
 config RTC_DRV_AT91RM9200
 	tristate "AT91RM9200 or some AT91SAM9 RTC"
-	depends on ARCH_AT91RM9200 || ARCH_AT91SAM9RL || ARCH_AT91SAM9G45
+	depends on ARCH_AT91
 	help
 	  Driver for the internal RTC (Realtime Clock) module found on
 	  Atmel AT91RM9200's and some  AT91SAM9 chips. On AT91SAM9 chips