brcmfmac: allow stopping netif queue for different reasons
Currently, the netif queue is only stopped when the bus interface is
giving a push back. This will change soon so prepare the driver by
adding a stop reason and stop/resume the queue accordingly.
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com> Reviewed-by: Hante Meuleman <meuleman@broadcom.com> Reviewed-by: Piotr Haber <phaber@broadcom.com> Signed-off-by: Arend van Spriel <arend@broadcom.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>