brcmfmac: fix for multiple netdevice interface support

brcmfmac: fix for multiple netdevice interface support

virtual netdevice interface like P2P client and GO need
different callbacks for .open and .down. This patch adds
those.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>