brcmfmac: remove reference to fwsignal data from struct brcmf_pub

The fwsignal module is part of the bcdc protocol and as such does
its instance data is not needed in core structure. Moving it into
struct brcmf_bcdc instead.

Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-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>