staging: pi433: eliminate a temporary variable

We can just get rid of the "spi_address".  It's not clear what the
"address" part of the name means, and the type should have been a u8.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>