mtd: spi-nor: Fix direction of the write_sr() transfer

write_sr() sends data to the SPI memory, fix the direction.

Fixes: b35b9a10 ("mtd: spi-nor: Move m25p80 code in spi-nor.c")
Reported-by: John Garry <john.garry@huawei.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Tested-by: John Garry <john.garry@huawei.com>
Acked-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>