spi: s3c64xx: clear loopback bit after loopback test

When SPI loopback transfer is performed, S3C64XX_SPI_MODE_SELF_LOOPBACK
bit still remained. It works as loopback even if the next transfer is
not spi loopback mode.
If not SPI_LOOP, needs to clear S3C64XX_SPI_MODE_SELF_LOOPBACK bit.

Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com>
Fixes: ffb7bcd ("spi: s3c64xx: support loopback mode")
Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Link: https://lore.kernel.org/r/20230711082020.138165-1-jaewon02.kim@samsung.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: jwn0222

drivers/spi/spi-s3c64xx.c

@@ -684,6 +684,8 @@ static int s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
 
 	if ((sdd->cur_mode & SPI_LOOP) && sdd->port_conf->has_loopback)
 		val |= S3C64XX_SPI_MODE_SELF_LOOPBACK;
+	else
+		val &= ~S3C64XX_SPI_MODE_SELF_LOOPBACK;
 
 	writel(val, regs + S3C64XX_SPI_MODE_CFG);