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_efi_loader.py b/test/py/tests/test_efi_loader.py
index ff880ff..58f2655 100644
--- a/test/py/tests/test_efi_loader.py
+++ b/test/py/tests/test_efi_loader.py
@@ -53,7 +53,7 @@
 """
 
 import pytest
-import u_boot_utils
+import utils
 
 PROTO_TFTP, PROTO_HTTP = range(0, 2)
 
@@ -132,7 +132,7 @@
 
     addr = f.get('addr', None)
     if not addr:
-        addr = u_boot_utils.find_ram_base(ubman)
+        addr = utils.find_ram_base(ubman)
 
     fn = f['fn']
     if proto == PROTO_TFTP: