JFFS2 FS might sometime provide kmap'd buffers as destination
buffers to read data from flash. Update spi_map_buf() function to
generate sg_list for such buffers, so that SPI controllers drivers can
use DMA to read data into such buffers.
Signed-off-by: NVignesh R <vigneshr@ti.com>
Signed-off-by: NMark Brown <broonie@kernel.org>