brcmfmac: update beacon IE after bss up and clear when AP stopped

Firmware doesn't update beacon/Probe Response vendor IEs correctly when
bss is down, so we move brcmf_config_ap_mgmt_ie after BSS up. And host
driver should clear IEs when AP stopped so that the IEs in host side will
be synced with in firmware side.

Signed-off-by: Wright Feng <wright.feng@cypress.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>