wlcore: don't bail out when beacon/probe resp are missing

On ap initialization, the ap rates are configured before
the beacon and probe-response are configured.

Trying to set the beacon/probe-response in this stage
results in bailing out from wl1271_bss_info_changed_ap,
before all the configurations took place.

Identify this case by checking explicitly for -ENOENT
return value when configuring the beacon/probe-response.

Signed-off-by: Eliad Peller <eliad@wizery.com>
mac80211: use short slot for ap on 11a channel (INTERNAL?)

ieee80211_change_bss is responsible for setting use_short_slot
when beaconing on 11a channel. However, since SET_BSS is called
before START_AP (which sets the channel), the channel is still
unknown at this stage.

Add a similar check for ieee80211_start_ap as well.

Signed-off-by: Eliad Peller <eliad@wizery.com>