brcmfmac: remove restriction from .sched_scan_start() callback

In the .sched_scan_start() callback a condition was checked whether a
normal scan was ongoing. However, there is no need for this check as
it is ok to start the scheduled scan irrespective whether or not a
normal scan is ongoing.

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>