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/binman/cbfs_util_test.py b/tools/binman/cbfs_util_test.py
index a929612..2c62c8a 100755
--- a/tools/binman/cbfs_util_test.py
+++ b/tools/binman/cbfs_util_test.py
@@ -19,8 +19,8 @@
 from binman import cbfs_util
 from binman.cbfs_util import CbfsWriter
 from binman import elf
-import test_util
-import tools
+from patman import test_util
+from patman import tools
 
 U_BOOT_DATA           = b'1234'
 U_BOOT_DTB_DATA       = b'udtb'