MAINTAINERS: add MT2712 RTC files

This patch add MT2712 RTC related files to MAINTAINERS file.
Signed-off-by: Ran Bi <ran.bi@mediatek.com>
Link: https://lore.kernel.org/r/20200226051303.22560-5-ran.bi@mediatek.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

MAINTAINERS

@@ -1995,7 +1995,9 @@ M:	Sean Wang <sean.wang@mediatek.com>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 L:	linux-mediatek@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
+F:	Documentation/devicetree/bindings/rtc/rtc-mt2712.txt
 F:	Documentation/devicetree/bindings/rtc/rtc-mt7622.txt
+F:	drivers/rtc/rtc-mt2712.c
 F:	drivers/rtc/rtc-mt6397.c
 F:	drivers/rtc/rtc-mt7622.c