mtd: rawnand: marvell: Minor documentation correction

Kernel test robot throws below warning ->
drivers/mtd/nand/raw/marvell_nand.c:454: warning: This comment starts
with '/**', but isn't a kernel-doc comment. Refer
Documentation/doc-guide/kernel-doc.rst

Minor documentation correction.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210607193736.4654-1-jrdr.linux@gmail.com