Input: rotary-encoder - refactor and clean up

Refactor state retrieval and event reporting in interrupt handler.
Remove a few empty lines.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>