brcmfmac: wait for firmware event when creating P2P_DEVICE interface

The firmware sends a IF event to notify the host driver that the
P2P_DEVICE interface has been created. Wait for the event before
returning the related wireless_dev.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Piotr Haber <phaber@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>