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/dtoc/fdt_util.py b/tools/dtoc/fdt_util.py
index f343166..f1f7056 100644
--- a/tools/dtoc/fdt_util.py
+++ b/tools/dtoc/fdt_util.py
@@ -13,8 +13,8 @@
 import sys
 import tempfile
 
-from patman import command
-from patman import tools
+from u_boot_pylib import command
+from u_boot_pylib import tools
 
 def fdt32_to_cpu(val):
     """Convert a device tree cell to an integer