staging: brcm80211: remove unnecessary abstraction for scheduler

The source dhd_linux_sched.c provided function setScheduler, but it
simply calls sched_setscheduler() linux function. The setScheduler()
function has been removed.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>