brcmfmac: add role attribute to struct brcmf_if_event definition

According specification the IF event has an additional field indicating
the role or type of the interface for which this event is sent.

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>