rtc: xgene: Set hardware dependency

The rtc-xgene driver is only useful on X-Gene SoC.

Signed-off-by: Jean Delvare <[e-mail]>
Cc: Alessandro Zummo <[e-mail]>
Cc: Alexandre Belloni <[e-mail]>
Cc: Iyappan Subramanian <[e-mail]>
Cc: Keyur Chudgar <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/Kconfig

···
 config RTC_DRV_XGENE
 	tristate "APM X-Gene RTC"
 	depends on HAS_IOMEM
+	depends on ARCH_XGENE || COMPILE_TEST
 	help
 	  If you say yes here you get support for the APM X-Gene SoC real time
 	  clock.