drm/bridge: cdns: remove set but not used variable 'nlanes'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/bridge/cdns-dsi.c: In function ‘cdns_dsi_mode2cfg’:
drivers/gpu/drm/bridge/cdns-dsi.c:515:11: warning: variable ‘nlanes’
set but not used [-Wunused-but-set-variable]

It is never used, and so can be removed.
Signed-off-by: yu kuai <yukuai3@huawei.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191226121415.39483-1-yukuai3@huawei.com

drivers/gpu/drm/bridge/cdns-dsi.c

@@ -512,7 +512,7 @@ static int cdns_dsi_mode2cfg(struct cdns_dsi *dsi,
 	struct cdns_dsi_output *output = &dsi->output;
 	unsigned int tmp;
 	bool sync_pulse = false;
-	int bpp, nlanes;
+	int bpp;
 
 	memset(dsi_cfg, 0, sizeof(*dsi_cfg));
 
@@ -520,7 +520,6 @@ static int cdns_dsi_mode2cfg(struct cdns_dsi *dsi,
 		sync_pulse = true;
 
 	bpp = mipi_dsi_pixel_format_to_bpp(output->dev->format);
-	nlanes = output->dev->lanes;
 
 	if (mode_valid_check)
 		tmp = mode->htotal -