brcmfmac: make internal escan more generic

For scheduled scan we initiate an escan in firmware to obtain more
info missing from the scheduled scan notification we get from firmware.
For upcoming functionality this is also required so make it a bit
more generic.

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>