staging: wfx: ensure that traces never modify arguments

There is no reason for a trace to change any bit of the argument. So,
let's make sure that is the case by declaring the arguments constant.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20191217161318.31402-22-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>