board: ti: am64x: Set storage_interface and fw_dev_part ENVs

When ICSSG driver is enabled (CONFIG_TI_ICSSG_PRUETH=y) set
storage_interface and fw_dev_part env variables.

These variables need be set appropriately in order to load different
ICSSG firmwares needed for ICSSG driver. By default the storage
interface is mmc and the partition is 1:2. User can modify this based on
their needs.

Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
diff --git a/board/ti/am64x/am64x.env b/board/ti/am64x/am64x.env
index 9a8812d..8ad805a 100644
--- a/board/ti/am64x/am64x.env
+++ b/board/ti/am64x/am64x.env
@@ -39,3 +39,8 @@
 	run get_kern_usb;
 	run get_fdt_usb;
 	run run_kern;
+
+#if CONFIG_TI_ICSSG_PRUETH
+storage_interface=mmc
+fw_dev_part=1:2
+#endif