staging: pi433: replace simple switch statements

Use const array to map switch cases to resulting values.

Signed-off-by: Valentin Vidic <Valentin.Vidic@CARNet.hr>
Reviewed-by: Marcus Wolf <Marcus.Wolf@Wolf-Entwicklungen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>