rtc: adjust MAINTAINERS entry

Add missing files to the RTC entry of MAINTAINERS
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

MAINTAINERS

@@ -9563,6 +9563,9 @@ F:	Documentation/rtc.txt
 F:	drivers/rtc/
 F:	include/linux/rtc.h
 F:	include/uapi/linux/rtc.h
+F:	include/linux/rtc/
+F:	include/linux/platform_data/rtc-*
+F:	tools/testing/selftests/timers/rtctest.c
 
 REALTEK AUDIO CODECS
 M:	Bard Liao <bardliao@realtek.com>