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_mmc_wr.py b/test/py/tests/test_mmc_wr.py
index 533bae0..41a75f8 100644
--- a/test/py/tests/test_mmc_wr.py
+++ b/test/py/tests/test_mmc_wr.py
@@ -6,7 +6,7 @@
 # to the eMMC or SD card, then reads it back and performs a comparison.
 
 import pytest
-import u_boot_utils
+import utils
 
 """
 This test relies on boardenv_* to containing configuration values to define
@@ -61,7 +61,7 @@
 
     count_bytes = count_sectors * 512
     bcfg = ubman.config.buildconfig
-    ram_base = u_boot_utils.find_ram_base(ubman)
+    ram_base = utils.find_ram_base(ubman)
     src_addr = '0x%08x' % ram_base
     dst_addr = '0x%08x' % (ram_base + count_bytes)