MAINTAINERS: Add entry for ATCRTC100 RTC driver

Add support entry for the Andes ATCRTC100 RTC driver in the
MAINTAINERS file.

Signed-off-by: CL Wang <cl634@andestech.com>
Link: https://patch.msgid.link/20250915031439.2680364-3-cl634@andestech.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: CL Wang

MAINTAINERS

@@ -3946,6 +3946,12 @@ F:	drivers/power/reset/atc260x-poweroff.c
 F:	drivers/regulator/atc260x-regulator.c
 F:	include/linux/mfd/atc260x/*
 
+ATCRTC100 RTC DRIVER
+M:	CL Wang <cl634@andestech.com>
+S:	Supported
+F:	Documentation/devicetree/bindings/rtc/andestech,atcrtc100.yaml
+F:	drivers/rtc/rtc-atcrtc100.c
+
 ATHEROS 71XX/9XXX GPIO DRIVER
 M:	Alban Bedel <albeu@free.fr>
 S:	Maintained