patman: Move to absolute imports

At present patman sets the python path on startup so that it can access
the libraries it needs. If we convert to use absolute imports this is not
necessary.

Move patman to use absolute imports. This requires changes in tools which
use the patman libraries (which is most of them).

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/func_test.py b/tools/patman/func_test.py
index 748e225..b7e2825 100644
--- a/tools/patman/func_test.py
+++ b/tools/patman/func_test.py
@@ -14,10 +14,10 @@
 
 from io import StringIO
 
-import gitutil
-import patchstream
-import settings
-import tools
+from patman import gitutil
+from patman import patchstream
+from patman import settings
+from patman import tools
 
 
 @contextlib.contextmanager