patman: Rename test.py to test_checkpatch.py

These tests check checkpatch.pl operation and can server as our tests for
the U-Boot-specific updates to that script. Rename the file and update
comments to indicate this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/main.py b/tools/patman/main.py
index 0df2aa5..28a9a26 100755
--- a/tools/patman/main.py
+++ b/tools/patman/main.py
@@ -25,7 +25,7 @@
 from patman import project
 from patman import settings
 from patman import terminal
-from patman import test
+from patman import test_checkpatch
 
 
 parser = OptionParser()
@@ -93,7 +93,7 @@
 
     sys.argv = [sys.argv[0]]
     result = unittest.TestResult()
-    for module in (test.TestPatch, func_test.TestFunctional):
+    for module in (test_checkpatch.TestPatch, func_test.TestFunctional):
         suite = unittest.TestLoader().loadTestsFromTestCase(module)
         suite.run(result)