staging:rtl8192u: Rename IsACValid and add parenthesis - Style

The macro IsACValid is renamed to resolve the checkpatch issue with
CamelCase naming. In addition the parameter has parenthesis added to
clear the checkpatch issue with precedence issues.

These changes are coding style changes and as such should have not
impact on runtime code execution.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>