mtd: rawnand: gpmi: remove unneeded variable

Return status directly from function called.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20211213112627.436745-1-chi.minghao@zte.com.cn