rndis_wlan: avoid uninitialized var warning in rndis_wlan_craft_connected_bss

  CC [M]  drivers/net/wireless/rndis_wlan.o
drivers/net/wireless/rndis_wlan.c: In function ‘rndis_wlan_craft_connected_bss’:
drivers/net/wireless/rndis_wlan.c:2542:2: warning: ‘ret’ may be used uninitialized in this function

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