MAINTAINERS: Add myself as reviewer for HYPERBUS

Add myself as Designated Reviewer for Hyperbus support.
I'm assessing the framework and I'd like to get involved
in reviewing further patches.

Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Acked-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230620025359.33839-1-tudor.ambarus@linaro.org