MAINTAINERS: adjust file entry in ARM/Mediatek RTC DRIVER

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 <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20240301145907.32732-1-lukas.bulwahn@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>