Pylint: allow using pass even when not strictly necessary

If we take the trouble of using pass, it's because we think the code
is clearer that way. For example, Pylint 2.4 rejects pass in

    def foo():
        """Do nothing."""
        pass

But relying on a docstring as the sole code is weird, hence the use of
pass.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

.pylintrc

@@ -55,7 +55,9 @@ max-module-lines=2000
 #        return value1
 #    else:
 #        return value2
-disable=logging-format-interpolation,no-else-return
+# * unnecessary-pass: If we take the trouble of adding a line with "pass",
+#   it's because we think the code is clearer that way.
+disable=logging-format-interpolation,no-else-return,unnecessary-pass
 
 [REPORTS]
 # Don't diplay statistics. Just the facts.