MAINTAINERS: Add PL353 NAND controller entry

Add Naga from Xilinx and myself responsible of this driver.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Naga Sureshkumar Relli <naga.sureshkumar.relli@xilinx.com>
Link: https://lore.kernel.org/linux-mtd/20210610082040.2075611-17-miquel.raynal@bootlin.com