omap-common: Common get_board_serial function to pass serial through ATAG

Since there is a common function to grab the serial number from the die id bits,
it makes sense have one to parse that serial number and feed it to the serial
ATAG.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/lge/sniper/sniper.c b/board/lge/sniper/sniper.c
index cdda76b..4eff01a 100644
--- a/board/lge/sniper/sniper.c
+++ b/board/lge/sniper/sniper.c
@@ -149,20 +149,7 @@
 
 void get_board_serial(struct tag_serialnr *serialnr)
 {
-	char *serial_string;
-	unsigned long long serial;
-
-	serial_string = getenv("serial#");
-
-	if (serial_string) {
-		serial = simple_strtoull(serial_string, NULL, 16);
-
-		serialnr->high = (unsigned int) (serial >> 32);
-		serialnr->low = (unsigned int) (serial & 0xffffffff);
-	} else {
-		serialnr->high = 0;
-		serialnr->low = 0;
-	}
+	omap_die_id_get_board_serial(serialnr);
 }
 
 void reset_misc(void)