binman: Move to absolute imports

At present binman 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 binman to use absolute imports. This enables removable of the path
adjusting in Entry also.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/cbfs_util.py b/tools/binman/cbfs_util.py
index 34c5116..f7c3cd0 100644
--- a/tools/binman/cbfs_util.py
+++ b/tools/binman/cbfs_util.py
@@ -20,8 +20,8 @@
 import struct
 import sys
 
+from binman import elf
 import command
-import elf
 import tools
 
 # Set to True to enable printing output while working