tests: don't allow to generate events of the same type subsequently

tests: don't allow to generate events of the same type subsequently

Since linux v5.1 the state of simulated lines is tracked by the kernel
and it's no longer possible to generate two subsequent events of the
same type (e.g. two rising edge events one after another). Drop the
event_type parameter from test_set_event() and adjust all users.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>