brcmfmac: handle firmware signalling destination entry state

Firmware can signal whether the host driver may sent packets for
a specific destination or interface. This can happen when a
destination is sleeping or when going off-channel.

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: John W. Linville <linville@tuxdriver.com>