mkimage: umount boot only in !beaglebone.

mkimage.sh.in

@@ -184,7 +184,9 @@ elif [ "$PLATFORM" = "odroid-u2" ]; then
     dd if=${ROOTFSDIR}/boot/E4412_S.tzsw.signed.bin of=${LOOPDEV} seek=2111 >/dev/null 2>&1
 fi
 
-mountpoint -q ${ROOTFSDIR}/boot || umount ${ROOTFSDIR}/boot
+if [ "$PLATFORM" != "beaglebone" ]; then
+    umount ${ROOTFSDIR}/boot
+fi
 umount $ROOTFSDIR
 partx -d $LOOPDEV
 losetup -d $LOOPDEV