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>

tools/binman/cbfs_util_test.py

@@ -16,9 +16,9 @@ import struct
 import tempfile
 import unittest
 
-import cbfs_util
-from cbfs_util import CbfsWriter
-import elf
+from binman import cbfs_util
+from binman.cbfs_util import CbfsWriter
+from binman import elf
 import test_util
 import tools