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>
diff --git a/tools/patman/patman.py b/tools/patman/patman.py
index cf53e53..7f4ac9a 100755
--- a/tools/patman/patman.py
+++ b/tools/patman/patman.py
@@ -93,7 +93,7 @@
         suite = unittest.TestLoader().loadTestsFromTestCase(module)
         suite.run(result)
 
-    for module in ['gitutil', 'settings']:
+    for module in ['gitutil', 'settings', 'terminal']:
         suite = doctest.DocTestSuite(module)
         suite.run(result)