drm/sun4i: sun6i_mipi_dsi: fix DCS long write packet length

The packet length of DCS long write packet should not be added with 1
when constructing long write packet.

Fix this.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191006160303.24413-4-icenowy@aosc.io

drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c

@@ -832,8 +832,8 @@ static u32 sun6i_dsi_dcs_build_pkt_hdr(struct sun6i_dsi *dsi,
 	u32 pkt = msg->type;
 
 	if (msg->type == MIPI_DSI_DCS_LONG_WRITE) {
-		pkt |= ((msg->tx_len + 1) & 0xffff) << 8;
-		pkt |= (((msg->tx_len + 1) >> 8) & 0xffff) << 16;
+		pkt |= ((msg->tx_len) & 0xffff) << 8;
+		pkt |= (((msg->tx_len) >> 8) & 0xffff) << 16;
 	} else {
 		pkt |= (((u8 *)msg->tx_buf)[0] << 8);
 		if (msg->tx_len > 1)