rndis_wlan: remove pointless check from rndis_scan()

In rndis_scan(), 'request' is actually always valid pointer and
the !request check is unneeded, so remove it.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>