mtd: rawnand: cadence: Remove an unneeded result variable

Return the value cadence_nand_set_access_width16() directly instead of
storing it in another redundant variable.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220901074555.313266-1-ye.xingchen@zte.com.cn