MAINTAINERS: add NXP S32G RTC driver

Add the NXP S32G RTC driver as maintained so further patches on this
driver can be reviewed under this architecture.

Signed-off-by: Ciprian Marian Costea <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

MAINTAINERS

···
 R:	NXP S32 Linux Team <[e-mail]>
 L:	[e-mail] (moderated for non-subscribers)
 S:	Maintained
+F:	Documentation/devicetree/bindings/rtc/nxp,s32g-rtc.yaml
 F:	arch/arm64/boot/dts/freescale/s32g*.dts*
 F:	drivers/pinctrl/nxp/
+F:	drivers/rtc/rtc-s32g.c
 
 ARM/NXP S32G/S32R DWMAC ETHERNET DRIVER
 M:	Jan Petrous <[e-mail]>