TODO

-Implement timeout in wait_for_message.
-Add support for erasing NAND.
-Add support for erasing and programming NOR.
-Display external commands error messages when failing.
-If we detect BOOTPSP, can we send a command to reboot?
 (just to make sure to send a fresh UBL).
-Add support to send UBL and APP in binary form with a
 CRC like the RBL does it.