brcmfmac: get rid of struct brcmf_cfg80211_info::active_scan field

The field struct brcmf_cfg80211_info::active_scan is set to true upon
initializing the driver instance, but it is never changed so simply
get rid of it.

Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>