mtd: Convert fallthrough comments into statements

Use Joe Perches cvt_fallthrough.pl script to convert

	/* fallthrough */

comments (and its derivatives) into a

	fallthrough;

statement. This automatically drops useless ones.

Do it MTD-wide.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Vignesh Raghavendra <vigneshr@ti.com>
Acked-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Richard Weinberger <richard@nod.at>
Link: https://lore.kernel.org/linux-mtd/20200325212115.14170-1-miquel.raynal@bootlin.com