drm/dsi: Make mipi_dsi_dcs_write() return ssize_t

This function returns the value of the struct mipi_dsi_host_ops'
.transfer() so make sure the return types are consistent.

Acked-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/gpu/drm/panel/panel-s6e8aa0.c b/drivers/gpu/drm/panel/panel-s6e8aa0.c
index 06e57a2..beb4349 100644
--- a/drivers/gpu/drm/panel/panel-s6e8aa0.c
+++ b/drivers/gpu/drm/panel/panel-s6e8aa0.c
@@ -133,14 +133,14 @@
 static void s6e8aa0_dcs_write(struct s6e8aa0 *ctx, const void *data, size_t len)
 {
 	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
-	int ret;
+	ssize_t ret;
 
 	if (ctx->error < 0)
 		return;
 
 	ret = mipi_dsi_dcs_write(dsi, dsi->channel, data, len);
 	if (ret < 0) {
-		dev_err(ctx->dev, "error %d writing dcs seq: %*ph\n", ret, len,
+		dev_err(ctx->dev, "error %zd writing dcs seq: %*ph\n", ret, len,
 			data);
 		ctx->error = ret;
 	}