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

test/py/tests/test_fs/conftest.py

@@ -8,7 +8,7 @@ import pytest
 import re
 from subprocess import call, check_call, check_output, CalledProcessError
 from fstest_defs import *
-import u_boot_utils as util
+import utils as util
 # pylint: disable=E0611
 from tests import fs_helper