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_zynqmp_secure.py b/test/py/tests/test_zynqmp_secure.py
index 7549e2c..c057e36 100644
--- a/test/py/tests/test_zynqmp_secure.py
+++ b/test/py/tests/test_zynqmp_secure.py
@@ -3,7 +3,7 @@
 
 import pytest
 import re
-import u_boot_utils
+import utils
 import test_net
 
 """
@@ -45,7 +45,7 @@
 
     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']
@@ -78,7 +78,7 @@
 
     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))
@@ -86,7 +86,7 @@
 
     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))