omap-common: Common function to display die id, replacing omap3-specific version

This introduces omap_die_id_display to display the full die id.
There is no need to store it in an environment variable, that no boot script
is using anyway.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/ti/beagle/beagle.c b/board/ti/beagle/beagle.c
index 149b5db..56e3cfe 100644
--- a/board/ti/beagle/beagle.c
+++ b/board/ti/beagle/beagle.c
@@ -494,7 +494,7 @@
 	writel(~(GPIO31 | GPIO30 | GPIO29 | GPIO28 | GPIO22 | GPIO21 |
 		GPIO15 | GPIO14 | GPIO13 | GPIO12), &gpio5_base->oe);
 
-	dieid_num_r();
+	omap_die_id_display();
 
 #ifdef CONFIG_VIDEO_OMAP3
 	beagle_dvi_pup();