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/toolchain.py b/tools/buildman/toolchain.py
index a354049..acb5a29 100644
--- a/tools/buildman/toolchain.py
+++ b/tools/buildman/toolchain.py
@@ -11,9 +11,9 @@
 import urllib.request, urllib.error, urllib.parse
 
 from buildman import bsettings
-import command
-import terminal
-import tools
+from patman import command
+from patman import terminal
+from patman import tools
 
 (PRIORITY_FULL_PREFIX, PRIORITY_PREFIX_GCC, PRIORITY_PREFIX_GCC_PATH,
     PRIORITY_CALC) = list(range(4))