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/technexion/twister/twister.c b/board/technexion/twister/twister.c
index a4aed3b..48d207f 100644
--- a/board/technexion/twister/twister.c
+++ b/board/technexion/twister/twister.c
@@ -92,7 +92,7 @@
 	struct tam3517_module_info info;
 	int ret;
 
-	dieid_num_r();
+	omap_die_id_display();
 
 	eth_addr = getenv("ethaddr");
 	if (eth_addr)