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_usb.py b/test/py/tests/test_usb.py
index 6247f92..1dcd083 100644
--- a/test/py/tests/test_usb.py
+++ b/test/py/tests/test_usb.py
@@ -4,7 +4,7 @@
 import pytest
 import random
 import re
-import u_boot_utils
+import utils
 
 """
 Note: This test doesn't rely on boardenv_* configuration values but it can
@@ -296,7 +296,7 @@
         pytest.skip('No %s partition detected' % fs.upper())
 
 def usb_fatload_fatwrite(ubman, fs, x, part):
-    addr = u_boot_utils.find_ram_base(ubman)
+    addr = utils.find_ram_base(ubman)
     size = random.randint(4, 1 * 1024 * 1024)
     output = ubman.run_command('crc32 %x %x' % (addr, size))
     m = re.search('==> (.+?)', output)
@@ -391,7 +391,7 @@
         pytest.skip('No %s partition detected' % fs.upper())
 
 def usb_ext4load_ext4write(ubman, fs, x, part):
-    addr = u_boot_utils.find_ram_base(ubman)
+    addr = utils.find_ram_base(ubman)
     size = random.randint(4, 1 * 1024 * 1024)
     output = ubman.run_command('crc32 %x %x' % (addr, size))
     m = re.search('==> (.+?)', output)
@@ -505,7 +505,7 @@
                 part_detect = 1
                 file, size, expected_crc32 = \
                     usb_ext4load_ext4write(ubman, fs, x, part)
-                addr = u_boot_utils.find_ram_base(ubman)
+                addr = utils.find_ram_base(ubman)
 
                 offset = random.randrange(128, 1024, 128)
                 output = ubman.run_command(
@@ -572,7 +572,7 @@
 
                 for part in partitions:
                     part_detect = 1
-                    addr = u_boot_utils.find_ram_base(ubman)
+                    addr = utils.find_ram_base(ubman)
 
                     if fs == 'fat':
                         file, size, expected_crc32 = \
@@ -618,7 +618,7 @@
 
                 for part in partitions:
                     part_detect = 1
-                    addr = u_boot_utils.find_ram_base(ubman)
+                    addr = utils.find_ram_base(ubman)
                     size = random.randint(4, 1 * 1024 * 1024)
                     file = '%s_%d' % ('uboot_test', size)