MAINTAINERS: Set myself as Goldfish RTC maintainer

While Goldfish platform is dusted, the RTC driver remains
valuable for us.

I'm volunteering to maintain goldfish RTC driver onward.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Miodrag Dinic <Miodrag.Dinic@syrmia.com>
Link: https://lore.kernel.org/r/20201114130921.651882-3-jiaxun.yang@flygoat.com

MAINTAINERS

@@ -1168,7 +1168,7 @@ F:	Documentation/devicetree/bindings/interrupt-controller/google,goldfish-pic.tx
 F:	drivers/irqchip/irq-goldfish-pic.c
 
 ANDROID GOLDFISH RTC DRIVER
-M:	Miodrag Dinic <miodrag.dinic@mips.com>
+M:	Jiaxun Yang <jiaxun.yang@flygoat.com>
 S:	Supported
 F:	Documentation/devicetree/bindings/rtc/google,goldfish-rtc.txt
 F:	drivers/rtc/rtc-goldfish.c