patman: Support erasing a previously unfinished text line

patman: Support erasing a previously unfinished text line

When printing progress it is useful to print a message and leave the
cursor at the end of the line until the operation is finished. When it is
finished, the line needs to be erased so a new line can start in its place.

Add a function to handle clearing a line previously written by
terminal.Print()

Signed-off-by: Simon Glass <sjg@chromium.org>