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_rd.py b/test/py/tests/test_mmc_rd.py
index 3c8356f..cd1e299 100644
--- a/test/py/tests/test_mmc_rd.py
+++ b/test/py/tests/test_mmc_rd.py
@@ -7,7 +7,7 @@
 
 import pytest
 import time
-import u_boot_utils
+import utils
 
 """
 This test relies on boardenv_* to containing configuration values to define
@@ -241,7 +241,7 @@
     bcfg = ubman.config.buildconfig
     has_cmd_memory = bcfg.get('config_cmd_memory', 'n') == 'y'
     has_cmd_crc32 = bcfg.get('config_cmd_crc32', 'n') == 'y'
-    ram_base = u_boot_utils.find_ram_base(ubman)
+    ram_base = utils.find_ram_base(ubman)
     addr = '0x%08x' % ram_base
 
     # Select MMC device