mtd: fix minor comment typo for struct mtd_master

Minor typo in the suspend description.

Signed-off-by: Marcel Hamer <marcel.hamer@windriver.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240216155022.79371-1-marcel.hamer@windriver.com