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/logicpd/am3517evm/am3517evm.c b/board/logicpd/am3517evm/am3517evm.c
index 24ff9c3..1f1e5ae 100644
--- a/board/logicpd/am3517evm/am3517evm.c
+++ b/board/logicpd/am3517evm/am3517evm.c
@@ -109,7 +109,7 @@
 	i2c_init(CONFIG_SYS_OMAP24_I2C_SPEED, CONFIG_SYS_OMAP24_I2C_SLAVE);
 #endif
 
-	dieid_num_r();
+	omap_die_id_display();
 
 	am3517_evm_musb_init();