test/py: do not import pytest multiple times

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
diff --git a/test/py/u_boot_utils.py b/test/py/u_boot_utils.py
index 9acb92d..6458449 100644
--- a/test/py/u_boot_utils.py
+++ b/test/py/u_boot_utils.py
@@ -11,7 +11,6 @@
 import pytest
 import sys
 import time
-import pytest
 
 def md5sum_data(data):
     """Calculate the MD5 hash of some data.