drm/i915/dsi: drop unused but set variable data

Prepare for re-enabling -Wunused-but-set-variable.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a1a167a4ff18b19d10769d83670e414586c16956.1685119007.git.jani.nikula@intel.com

drivers/gpu/drm/i915/display/vlv_dsi.c

@@ -136,7 +136,7 @@ static ssize_t intel_dsi_host_transfer(struct mipi_dsi_host *host,
 	enum port port = intel_dsi_host->port;
 	struct mipi_dsi_packet packet;
 	ssize_t ret;
-	const u8 *header, *data;
+	const u8 *header;
 	i915_reg_t data_reg, ctrl_reg;
 	u32 data_mask, ctrl_mask;
 
@@ -145,7 +145,6 @@ static ssize_t intel_dsi_host_transfer(struct mipi_dsi_host *host,
 		return ret;
 
 	header = packet.header;
-	data = packet.payload;
 
 	if (msg->flags & MIPI_DSI_MSG_USE_LPM) {
 		data_reg = MIPI_LP_GEN_DATA(port);