tools: kwboot: Print newline on error when progress was not completed

tools: kwboot: Print newline on error when progress was not completed

When progress was not completed, current terminal position is in progress
bar. So print newline before printing error message to make error message
more readable.

Signed-off-by: Pali Rohár <[email protected]>
Reviewed-by: Marek Behún <[email protected]>
Reviewed-by: Stefan Roese <[email protected]>