staging: pi433: fix CamelCase for regValue

Local variable storing the new value for dio register
so replace with dio_value.  Update regaddr to dio_addr
to match.

Fixes checkpatch warnings:

  CHECK: Avoid CamelCase: <regValue>

Signed-off-by: Valentin Vidic <Valentin.Vidic@CARNet.hr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>