MAINTAINERS: Add myself as co-maintainer of the Arasan NAND controller driver

When I submitted the driver I added Naga as Maintainer and forgot to
add myself.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210505213750.257417-20-miquel.raynal@bootlin.com

MAINTAINERS

@@ -1311,6 +1311,7 @@ W:	http://www.aquantia.com
 F:	drivers/net/ethernet/aquantia/atlantic/aq_ptp*
 ARASAN NAND CONTROLLER DRIVER
+M:	Miquel Raynal <miquel.raynal@bootlin.com>
 M:	Naga Sureshkumar Relli <nagasure@xilinx.com>
 L:	linux-mtd@lists.infradead.org
 S:	Maintained