staging: pi433: Remove SET_CHECKED usage from pi433_probe

SET_CHECKED returns from the function on failure and in pi433_probe it is
necessary to free the GPIOs and the device on failure.

Signed-off-by: Simon Sandström <simon@nikanor.nu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>