wifi: wilc1000: remove redundant ret variable

Return value from cfg80211_rx_mgmt() directly instead of
taking this in another redundant variable.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Jinpeng Cui <cui.jinpeng2@zte.com.cn>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220830105505.287564-1-cui.jinpeng2@zte.com.cn