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/buildman/main.py b/tools/buildman/main.py
index 94d495c4..52a83fc 100755
--- a/tools/buildman/main.py
+++ b/tools/buildman/main.py
@@ -25,9 +25,9 @@
 from buildman import cmdline
 from buildman import control
 from buildman import toolchain
-import patchstream
-import gitutil
-import terminal
+from patman import patchstream
+from patman import gitutil
+from patman import terminal
 
 def RunTests(skip_net_tests):
     import func_test