brcmfmac: keep ARP and ND offload enabled during WOWL

Currently ARP and ND (IPv6 Neigbor Discovery) offload get disabled
on entering suspend. However when firmwares support the wowl_cap
iovar then these offload routines can be kept enabled as they
will work during WOWL as well.

Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>