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/gitutil.py

@@ -5,9 +5,9 @@
 import os
 import sys
 
-from patman import command
 from patman import settings
-from patman import terminal
+from u_boot_pylib import command
+from u_boot_pylib import terminal
 
 # True to use --no-decorate - we check this in setup()
 use_no_decorate = True