beaglebone: adds barebox bootloader

jkt: This is a port of https://patchwork.ozlabs.org/patch/614226/

Change-Id: I646d843fe2b9248d5a2ed3855142f1545b7bab52
Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz>
diff --git a/board/czechlight_beaglebone/barebox.env/boot/sd b/board/czechlight_beaglebone/barebox.env/boot/sd
new file mode 100644
index 0000000..0cd1be6
--- /dev/null
+++ b/board/czechlight_beaglebone/barebox.env/boot/sd
@@ -0,0 +1,11 @@
+#!/bin/sh
+
+global.bootm.image=/boot/zImage
+
+# Default to using the barebox built-in dtb
+# global.bootm.oftree=/boot/oftree
+
+# No initrd
+# global.bootm.initrd=<path to initrd>
+
+global.linux.bootargs.dyn.root="root=/dev/mmcblk0p2 rootfstype=ext4 rootwait"