ARM: DRA7: Set serial number environment variable

This patch populates serial number environment variable from
die_id_0 and die_id_1 register values for DRA7xx boards.

The function is added in omap common code so that this can be re-used.

Serial# environment variable will be useful to show correct
information in "fastboot devices" commands.

Ref:
http://git.omapzoom.org/?p=repo/u-boot.git;a=commit;h=a6bcaaf67f6e4bcd97808f53d0ceb4b0c04d583c

Signed-off-by: Angela Stegmaier <angelabaker@ti.com>
Signed-off-by: Dileep Katta <dileep.katta@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/ti/dra7xx/evm.c b/board/ti/dra7xx/evm.c
index c101928..d464855 100644
--- a/board/ti/dra7xx/evm.c
+++ b/board/ti/dra7xx/evm.c
@@ -93,10 +93,16 @@
 int board_late_init(void)
 {
 #ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
+	u32 id[4];
+
 	if (omap_revision() == DRA722_ES1_0)
 		setenv("board_name", "dra72x");
 	else
 		setenv("board_name", "dra7xx");
+
+	id[0] = readl((*ctrl)->control_std_fuse_die_id_0);
+	id[1] = readl((*ctrl)->control_std_fuse_die_id_1);
+	usb_set_serial_num_from_die_id(id);
 #endif
 	return 0;
 }