OMAPDSS: add pdata->default_display_name

We can currently set the default display (i.e. the initial display) in
the omapdss platform data by using a pointer to the default
omap_dss_device. Internally omapdss uses the device's name to resolve
the default display.

As it's difficult to get the omap_dss_device pointer in the future,
after we've changed the omapdss device model, this patch adds a new way
to define the default display, by using the name of the display.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Archit Taneja <archit@ti.com>
diff --git a/include/video/omapdss.h b/include/video/omapdss.h
index aeb4e9a..6462f68 100644
--- a/include/video/omapdss.h
+++ b/include/video/omapdss.h
@@ -365,6 +365,7 @@
 	int num_devices;
 	struct omap_dss_device **devices;
 	struct omap_dss_device *default_device;
+	const char *default_display_name;
 	int (*dsi_enable_pads)(int dsi_id, unsigned lane_mask);
 	void (*dsi_disable_pads)(int dsi_id, unsigned lane_mask);
 	int (*set_min_bus_tput)(struct device *dev, unsigned long r);