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_fpga.py b/test/py/tests/test_fpga.py
index 7450b13..74cd42b 100644
--- a/test/py/tests/test_fpga.py
+++ b/test/py/tests/test_fpga.py
@@ -8,7 +8,7 @@
 import pytest
 import re
 import random
-import u_boot_utils
+import utils
 
 """
 Note: This test relies on boardenv_* containing configuration values to define
@@ -518,7 +518,7 @@
 
     addr = f.get('addr', None)
     if not addr:
-      addr = u_boot_utils.find_ram_base(ubman)
+      addr = utils.find_ram_base(ubman)
 
     expected_tftp = 'Bytes transferred = '
     fn = f['fn']
@@ -546,7 +546,7 @@
 
     keyaddr = f.get('keyaddr', None)
     if not keyaddr:
-      addr = u_boot_utils.find_ram_base(ubman)
+      addr = utils.find_ram_base(ubman)
     expected_tftp = 'Bytes transferred = '
     keyfn = f['keyfn']
     output = ubman.run_command('tftpboot %x %s' % (keyaddr, keyfn))
@@ -554,7 +554,7 @@
 
     addr = f.get('addr', None)
     if not addr:
-      addr = u_boot_utils.find_ram_base(ubman)
+      addr = utils.find_ram_base(ubman)
     expected_tftp = 'Bytes transferred = '
     fn = f['enckupfn']
     output = ubman.run_command('tftpboot %x %s' % (addr, fn))