spi: rspi: Add support for LSB-first word order

All RSPI variants support selecting the word order.
Advertize support for LSB-first order, and act upon the flag being set.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200218105810.902-3-geert+renesas@glider.beSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rspi.c

@@ -933,6 +933,8 @@ static int rspi_prepare_message(struct spi_controller *ctlr,
 		rspi->spcmd |= SPCMD_CPOL;
 	if (spi->mode & SPI_CPHA)
 		rspi->spcmd |= SPCMD_CPHA;
+	if (spi->mode & SPI_LSB_FIRST)
+		rspi->spcmd |= SPCMD_LSBF;
 
 	/* Configure slave signal to assert */
 	rspi->spcmd |= SPCMD_SSLA(spi->cs_gpiod ? rspi->ctlr->unused_native_cs
@@ -1255,7 +1257,8 @@ static int rspi_probe(struct platform_device *pdev)
 	ctlr->transfer_one = ops->transfer_one;
 	ctlr->prepare_message = rspi_prepare_message;
 	ctlr->unprepare_message = rspi_unprepare_message;
-	ctlr->mode_bits = SPI_CPHA | SPI_CPOL | SPI_LOOP | ops->extra_mode_bits;
+	ctlr->mode_bits = SPI_CPHA | SPI_CPOL | SPI_LSB_FIRST | SPI_LOOP |
+			  ops->extra_mode_bits;
 	ctlr->flags = ops->flags;
 	ctlr->dev.of_node = pdev->dev.of_node;
 	ctlr->use_gpio_descriptors = true;