buildman: Rename the main module

Python does not like the module name being the same as the module
directory. To allow buildman modules to be used from other tools, rename
it.

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

diff --git a/tools/buildman/buildman b/tools/buildman/buildman
index e4fba2d4b03b785f50033c817bba292f0c8ee960..11a5d8e18ab71465be9424cf930c5e792c75edb7 120000 (symlink)
--- a/tools/buildman/buildman
+++ b/tools/buildman/buildman
@@ -1 +1 @@
-buildman.py
\ No newline at end of file
+main.py
\ No newline at end of file

diff --git a/tools/buildman/buildman.py b/tools/buildman/main.py
similarity index 100%
rename from tools/buildman/buildman.py
rename to tools/buildman/main.py