sign_encrypt.py: make logger global

Makes the logger variable global to avoid passing it to all functions
that needs to log something.

Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/scripts/sign_encrypt.py b/scripts/sign_encrypt.py
index d89833f..8893b02 100755
--- a/scripts/sign_encrypt.py
+++ b/scripts/sign_encrypt.py
@@ -29,7 +29,7 @@
     return int(str, 0)
 
 
-def get_args(logger):
+def get_args():
     from argparse import ArgumentParser, RawDescriptionHelpFormatter
     import textwrap
     command_base = ['sign-enc', 'digest', 'stitch', 'verify']
@@ -180,9 +180,10 @@
     import struct
 
     logging.basicConfig()
+    global logger
     logger = logging.getLogger(os.path.basename(__file__))
 
-    args = get_args(logger)
+    args = get_args()
 
     if args.key.startswith('arn:'):
         from sign_helper_kms import _RSAPrivateKeyInKMS