mtd: spi_nor: pass DMA-able buffer to spi_nor_read_raw()

spi_nor_read_raw() calls nor->read() which might be implemented
by the m25p80 driver. m25p80 uses the spi-mem layer which requires
DMA-able in/out buffers. Pass kmalloc'ed dma buffer to spi_nor_read_raw().

Fixes: b038e8e3 ("mtd: spi-nor: parse SFDP Sector Map Parameter Table")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>