brcmfmac: wrap brcmf_fws_del_interface into bcdc layer

Create a new protocol interface function brcmf_proto_del_if for core
module to notify protocol layer upon interface deletion.

Signed-off-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>