patman: Move library functions into a library directory

The patman directory has a number of modules which are used by other tools
in U-Boot. This makes it hard to package the tools using pypi since the
common files must be copied along with the tool that uses them.

To address this, move these files into a new u_boot_pylib library. This
can be packaged separately and listed as a dependency of each tool.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/patman/patchstream.py

@@ -14,10 +14,10 @@ import queue
 import shutil
 import tempfile
 
-from patman import command
 from patman import commit
 from patman import gitutil
 from patman.series import Series
+from u_boot_pylib import command
 
 # Tags that we detect and remove
 RE_REMOVE = re.compile(r'^BUG=|^TEST=|^BRANCH=|^Review URL:'