Solved! guys. The problem was my USB TTL does not send enough power on 3.3 volt. As soons as I use an external power source with 3.3 Volt and enough power, the SFP booted OK and I benn able to send uboot (1224ABORT.bin) and unlock the bootloader.
Advise to others: If the uboot log on does not show the boot adress, like below:
Now running in RAM - U-Boot at: 83fc8000
Then, mybe the cause is that not enough power is provided to the sfp.