Don't use sample.ekl and sample.seq by default.

The sample files are just for testing. Using them by default could hide
from the user that they are calling the script wrong. Make it required
to supply the .ekl and .seq files.
Signed-off-by: Grant Likely <grant.likely@arm.com>

parser.py

@@ -604,12 +604,8 @@ if __name__ == '__main__':
         '--uniq', action='store_true', help='Collapse duplicates')
     parser.add_argument(
         '--print', action='store_true', help='Print results to stdout')
-    parser.add_argument(
-        'log_file', nargs='?', default='sample.ekl',
-        help='Input .ekl filename')
-    parser.add_argument(
-        'seq_file', nargs='?', default='sample.seq',
-        help='Input .seq filename')
+    parser.add_argument('log_file', help='Input .ekl filename')
+    parser.add_argument('seq_file', help='Input .seq filename')
     parser.add_argument('find_key', nargs='?', help='Search key')
     parser.add_argument('find_value', nargs='?', help='Search value')