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: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NTudor Ambarus <tudor.ambarus@microchip.com>
Tested-by: NJohn Garry <john.garry@huawei.com>
Acked-by: NVignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>