drm/tinydrm/mipi-dbi: Move cmdlock mutex init

cmdlock protects command execution so put it in mipi_dbi_spi_init()
where it conceptually belongs.
This is prep work for the splitting of struct mipi_dbi.
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190722104312.16184-2-noralf@tronnes.org

drivers/gpu/drm/tinydrm/mipi-dbi.c

@@ -506,8 +506,6 @@ int mipi_dbi_init_with_formats(struct mipi_dbi *mipi,
 	if (!mipi->command)
 		return -EINVAL;
 
-	mutex_init(&mipi->cmdlock);
-
 	mipi->tx_buf = devm_kmalloc(drm->dev, tx_buf_size, GFP_KERNEL);
 	if (!mipi->tx_buf)
 		return -ENOMEM;
@@ -1120,6 +1118,8 @@ int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *mipi,
 			return -ENOMEM;
 	}
 
+	mutex_init(&mipi->cmdlock);
+
 	DRM_DEBUG_DRIVER("SPI speed: %uMHz\n", spi->max_speed_hz / 1000000);
 
 	return 0;