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/test.py b/tools/patman/test.py
index 889e186..e7f709e 100644
--- a/tools/patman/test.py
+++ b/tools/patman/test.py
@@ -8,11 +8,11 @@
 import tempfile
 import unittest
 
-import checkpatch
-import gitutil
-import patchstream
-import series
-import commit
+from patman import checkpatch
+from patman import gitutil
+from patman import patchstream
+from patman import series
+from patman import commit
 
 
 class TestPatch(unittest.TestCase):