MAINTAINERS: Add drivers/clocksource to TIMEKEEPING

It's not a random dump ground and we care about it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>

MAINTAINERS

@@ -5431,6 +5431,7 @@ F:	include/linux/timex.h
 F:	kernel/time/clocksource.c
 F:	kernel/time/time*.c
 F:	kernel/time/ntp.c
+F:	drivers/clocksource
 
 TLG2300 VIDEO4LINUX-2 DRIVER
 M:	Huang Shijie <shijie8@gmail.com>