Starting from revision F we can toggle a GPIO to control nWP of
the NAND chip. This means that during power-on or other mode of
operation no changes can be done to the flash.
Remove the nWP before we try to write to the flash in the UART
mode. Leave it enabled for further operations.
Do not block the boot process for five seconds or longer. When
adding the configurable timeout the other timeout code got broken.
Remove it and instead supply uart_recv_bytes with the timeout per
charachter.
Holger Hans Peter Freyther