wcn36xx: send bss_type in scan requests

Pass the bss_type of the currently configured BSS in the message for the
scan request. Therefore, that setting needs to be kept in struct
wcn36xx_vif.

This seems to be only interesting when scanning for a specific SSID
and doesn't matter for regular wildcard scans.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>