brcmfmac: remove unused struct brcmf_sdio_dev::func_cis_ptr attribute

During the SDIO probe the func_cis_ptr attribute in struct brcmf_sdio_dev
is being determined, but it is never used after that. Removing it also
obsoletes two functions in bcmsdh.c.

Reviewed-by: Franky Lin <frankyl@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>