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>
diff --git a/tools/buildman/func_test.py b/tools/buildman/func_test.py
index cf91c33..ebd78f2 100644
--- a/tools/buildman/func_test.py
+++ b/tools/buildman/func_test.py
@@ -14,11 +14,11 @@
 from buildman import cmdline
 from buildman import control
 from buildman import toolchain
-from patman import command
 from patman import gitutil
-from patman import terminal
-from patman import test_util
-from patman import tools
+from u_boot_pylib import command
+from u_boot_pylib import terminal
+from u_boot_pylib import test_util
+from u_boot_pylib import tools
 
 settings_data = '''
 # Buildman settings file