staging: ozwpan: remove redundant NULL check for devs

The "devs" is a pointer to g_net_dev in ozmain.c.
g_net_dev has a default value as empty string.
So "devs" cannot be NULL, removes NULL check for "devs".

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>