board: toradex: verdin-imx8mm: add MAINTAINERS

Assign Igor Opaniuk as a board maintainer.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>

board/toradex/verdin-imx8mm/MAINTAINERS

+Verdin iMX8M Mini
+M:	Igor Opaniuk <igor.opaniuk@toradex.com>
+W:	https://www.toradex.com/computer-on-modules/verdin-arm-family/nxp-imx-8m-mini
+S:	Maintained
+F:	arch/arm/dts/imx8mm-verdin.dts
+F:	arch/arm/dts/imx8mm-verdin-u-boot.dtsi
+F:	board/toradex/verdin-imx8mm/
+F:	configs/verdin-imx8mm_defconfig
+F:	include/configs/verdin-imx8mm.h