staging: wlan-ng: remove unnecessary parenthesis in prism2fw.c

This patch removes unnecessary parentheses in different statements of
prism2fw.c file in order to to comply with the standard kernel
coding style.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>