brcmfmac: change the order of things in brcmf_detach()

When brcmf_detach() from the bus layer upon rmmod we can no longer
communicate. Hence we will set the bus state to DOWN and cleanup
the event and protocol layer. The network interfaces need to be
deleted before brcmf_cfg80211_detach() because the latter does the
wiphy_unregister() which issues a warning if there are still network
devices linked to the wiphy instance.

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>
Tested-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>