drm/panel: s6e63m0: Simplify SPI writing

This writing code is equivalent to the spi_write()
helper in the SPI framework. Insert a comment
that this will always work fine since SPI buffers
are in native endianness.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Stephan Gerhold <stephan@gerhold.net>
Cc: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201110234653.2248594-2-linus.walleij@linaro.org

drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c

@@ -25,16 +25,9 @@ static int s6e63m0_spi_dcs_read(struct device *dev, const u8 cmd, u8 *data)
 static int s6e63m0_spi_write_word(struct device *dev, u16 data)
 {
 	struct spi_device *spi = to_spi_device(dev);
-	struct spi_transfer xfer = {
-		.len	= 2,
-		.tx_buf = &data,
-	};
-	struct spi_message msg;
 
-	spi_message_init(&msg);
-	spi_message_add_tail(&xfer, &msg);
-
-	return spi_sync(spi, &msg);
+	/* SPI buffers are always in CPU order */
+	return spi_write(spi, &data, 2);
 }
 
 static int s6e63m0_spi_dcs_write(struct device *dev, const u8 *data, size_t len)