test/py: Drop u_boot_ prefix on test files

We know this is U-Boot so the prefix serves no purpose other than to
make things longer and harder to read. Drop it and rename the files.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com> # test_android / test_dfu
diff --git a/test/py/tests/test_android/test_ab.py b/test/py/tests/test_android/test_ab.py
index 739b7ce..5876a13 100644
--- a/test/py/tests/test_android/test_ab.py
+++ b/test/py/tests/test_android/test_ab.py
@@ -5,7 +5,7 @@
 
 import os
 import pytest
-import u_boot_utils
+import utils
 
 class ABTestDiskImage(object):
     """Disk Image used by the A/B tests."""
@@ -25,7 +25,7 @@
         persistent = ubman.config.persistent_data_dir + '/' + filename
         self.path = ubman.config.result_dir  + '/' + filename
 
-        with u_boot_utils.persistent_file_helper(ubman.log, persistent):
+        with utils.persistent_file_helper(ubman.log, persistent):
             if os.path.exists(persistent):
                 ubman.log.action('Disk image file ' + persistent +
                     ' already exists')
@@ -35,16 +35,16 @@
                 os.ftruncate(fd, 524288)
                 os.close(fd)
                 cmd = ('sgdisk', persistent)
-                u_boot_utils.run_and_log(ubman, cmd)
+                utils.run_and_log(ubman, cmd)
 
                 cmd = ('sgdisk', '--new=1:64:512', '--change-name=1:misc',
                     persistent)
-                u_boot_utils.run_and_log(ubman, cmd)
+                utils.run_and_log(ubman, cmd)
                 cmd = ('sgdisk', '--load-backup=' + persistent)
-                u_boot_utils.run_and_log(ubman, cmd)
+                utils.run_and_log(ubman, cmd)
 
         cmd = ('cp', persistent, self.path)
-        u_boot_utils.run_and_log(ubman, cmd)
+        utils.run_and_log(ubman, cmd)
 
 di = None
 @pytest.fixture(scope='function')