bindings: python: tests: make EventType private to prevent export

bindings: python: tests: make EventType private to prevent export

Previously, both tests_edge_event and tests_info_event had a public
module level EventType member.

The __main__ module for unittests does a star import from both modules
which led to an import conflict between the two.

It is not necessary to import EventType to run unit tests.

Now, EventType is private to avoid being imported via star syntax.

Signed-off-by: Vincent Fazio <vfazio@xes-inc.com>
Link: https://lore.kernel.org/r/20241114145116.2123714-18-vfazio@xes-inc.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>