MAINTAINERS: adjust file entry in ARM/Mediatek RTC DRIVER

Commit e8c0498505b0 ("dt-bindings: rtc: convert MT2717 RTC to the
json-schema") and commit aef3952ec13f ("dt-bindings: rtc: convert MT7622
RTC to the json-schema") convert rtc-mt{2712,7622}.txt to
mediatek,mt{2712,7622}-rtc.yaml, but misses to adjust the file entries in
MAINTAINERS.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains about a
broken reference.

Repair these file entries in ARM/Mediatek RTC DRIVER.

Signed-off-by: Lukas Bulwahn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

MAINTAINERS

···
 L:	[e-mail] (moderated for non-subscribers)
 L:	[e-mail] (moderated for non-subscribers)
 S:	Maintained
-F:	Documentation/devicetree/bindings/rtc/rtc-mt2712.txt
-F:	Documentation/devicetree/bindings/rtc/rtc-mt7622.txt
+F:	Documentation/devicetree/bindings/rtc/mediatek,mt2712-rtc.yaml
+F:	Documentation/devicetree/bindings/rtc/mediatek,mt7622-rtc.yaml
 F:	drivers/rtc/rtc-mt2712.c
 F:	drivers/rtc/rtc-mt6397.c
 F:	drivers/rtc/rtc-mt7622.c