spi: Get spi-3wire from dts

spi-3wire is used when SI/SO signals shared so get
the same from dts node and assign to mode on slave
plat->mode.

Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Jagan Teki <jteki@openedev.com>

drivers/spi/spi-uclass.c

@@ -378,6 +378,8 @@ int spi_slave_ofdata_to_platdata(const void *blob, int node,
 		mode |= SPI_CPHA;
 	if (fdtdec_get_bool(blob, node, "spi-cs-high"))
 		mode |= SPI_CS_HIGH;
+	if (fdtdec_get_bool(blob, node, "spi-3wire"))
+		mode |= SPI_3WIRE;
 	if (fdtdec_get_bool(blob, node, "spi-half-duplex"))
 		mode |= SPI_PREAMBLE;
 	plat->mode = mode;