rtc: move RTC_LIB_KUNIT_TEST to proper location

Move RTC_LIB_KUNIT_TEST under RTC_LIB so it is clear in the menu this is
part of the RTC subsystem.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210810212008.631359-2-alexandre.belloni@bootlin.com
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 763d362..5ceeafe 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -15,6 +15,8 @@
 rtc-core-$(CONFIG_RTC_INTF_PROC)	+= proc.o
 rtc-core-$(CONFIG_RTC_INTF_SYSFS)	+= sysfs.o
 
+obj-$(CONFIG_RTC_LIB_KUNIT_TEST)	+= lib_test.o
+
 # Keep the list ordered.
 
 obj-$(CONFIG_RTC_DRV_88PM80X)	+= rtc-88pm80x.o
@@ -178,4 +180,3 @@
 obj-$(CONFIG_RTC_DRV_X1205)	+= rtc-x1205.o
 obj-$(CONFIG_RTC_DRV_XGENE)	+= rtc-xgene.o
 obj-$(CONFIG_RTC_DRV_ZYNQMP)	+= rtc-zynqmp.o
-obj-$(CONFIG_RTC_LIB_KUNIT_TEST)	+= lib_test.o