MAINTAINERS: Add entry for Congatec Board Controller

Add the Congatec Board Controller drivers and header as Maintained by
myself.

Acked-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
Link: https://lore.kernel.org/r/20241001-congatec-board-controller-v3-5-39ceceed5c47@bootlin.com


Signed-off-by: Lee Jones <lee@kernel.org>