Configure rollback support

Add a symlink to rollback configuration to enable the bootloader to access
it should rollback be required.

Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>

scripts/setup-uboot-bootloader.sh

@@ -11,6 +11,7 @@ mkdir -p ${ROOTDIR}/boot/extlinux
 mkdir -p ${ROOTDIR}/boot/loader.0
 ln -s loader.0  ${ROOTDIR}/boot/loader
 ln -s ../loader/extlinux.conf ${ROOTDIR}/boot/extlinux/extlinux.conf
+ln -s ../loader/extlinux-rollback.conf ${ROOTDIR}/boot/extlinux/extlinux-rollback.conf
 cat << EOF > ${ROOTDIR}/boot/extlinux/extlinux.conf
 menu title Apertis OStree image
 timeout 10