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

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

drivers/gpu/drm/bridge/cdns-dsi.c: In function
‘cdns_dsi_bridge_enable’:
drivers/gpu/drm/bridge/cdns-dsi.c:788:6: warning: variable ‘bpp’
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/20191226121207.2099-1-yukuai3@huawei.com

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

@@ -785,13 +785,12 @@ static void cdns_dsi_bridge_enable(struct drm_bridge *bridge)
 	unsigned long tx_byte_period;
 	struct cdns_dsi_cfg dsi_cfg;
 	u32 tmp, reg_wakeup, div;
-	int bpp, nlanes;
+	int nlanes;
 
 	if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0))
 		return;
 
 	mode = &bridge->encoder->crtc->state->adjusted_mode;
-	bpp = mipi_dsi_pixel_format_to_bpp(output->dev->format);
 	nlanes = output->dev->lanes;
 
 	WARN_ON_ONCE(cdns_dsi_check_conf(dsi, mode, &dsi_cfg, false));