brcmfmac: remove condition for calling event handler

In fweh module the event handler was only called if the
struct brcmf_if instance had a non-null netdev associated.
This restriction is no longer valid for P2P_DEVICE type
of interface. This patch removes that restriction.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@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>